Organometallic compound and organic light-emitting device including the same

ABSTRACT

An organometallic compound represented by Formula 1:
 
M(L 1 ) n1 (L 2 ) n2   Formula 1
         wherein in Formula 1, M, L 1 , L 2 , n1, and n2 are the same as described in the specification.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2015-0017475, filed on Feb. 4, 2015, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

1. Field

The present disclosure relates to an organometallic compound and an organic light-emitting device including the same.

2. Description of the Related Art

Organic light emitting devices (OLEDs) are self-emission devices that have wide viewing angles, high contrast ratios, and short response times. In addition, OLEDs exhibit excellent brightness, driving voltage, and response speed characteristics, and produce full-color images.

A typical organic light-emitting device includes an anode, a cathode, and an organic layer that is disposed between the anode and the cathode and includes an emission layer. A hole transport region may be disposed between the anode and the emission layer, and an electron transport region may be disposed between the emission layer and the cathode. Holes provided from the anode may move toward the emission layer through the hole transport region, and electrons provided from the cathode may move toward the emission layer through the electron transport region. The holes and the electrons are recombined in the emission layer to produce excitons. These excitons change from an excited state to a ground state, thereby generating light.

Various types of organic light emitting devices are known. However, there still remains a need in OLEDs having low driving voltage, high efficiency, high brightness, and long lifespan.

SUMMARY

One or more embodiments relate to a novel organometallic compound and an organic light-emitting device including the same.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented exemplary embodiments.

Provided is an organometallic compound represented by Formula 1:

M in Formula 1 may be selected from Ir, Pt, Os, Ti, Zr, Hf, Eu, Tb, Tm, and Rh,

-   -   L₁ in Formula 1 is selected from ligands represented by Formula         2A, and n1 is 1, 2 or 3, and when n1 is 2 or greater, two or         more groups L₁ may be identical to or different from each other,     -   L₂ in Formula 1 may be selected from a monovalent organic         ligand, a divalent organic ligand, a trivalent organic ligand,         and a tetravalent organic ligand, and n2 is 0, 1, 2, 3 or 4, and         when n2 is 2 or greater, two or more L₂(s) may be identical to         or different from each other,     -   L₁ and L₂ in Formula 1 may be different from each other,     -   R₁, R₂ and R₁₁ to R₁₅ in Formula 2A may be each independently         selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, —SF₅, a         hydroxyl group, a cyano group, a nitro group, an amino group, an         amidino group, a hydrazine group, a hydrazone group, a         carboxylic acid group or a salt thereof, a sulfonic acid group         or a salt thereof, a phosphoric acid group or a salt thereof, a         substituted or unsubstituted C₁-C₆₀ alkyl group, a substituted         or unsubstituted C₂-C₆₀ alkenyl group, a substituted or         unsubstituted C₂-C₆₀ alkynyl group, a substituted or         unsubstituted C₁-C₆₀ alkoxy group, a substituted or         unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or         unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or         unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or         unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or         unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted         C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀         arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl         group, a substituted or unsubstituted monovalent non-aromatic         condensed polycyclic group, a substituted or unsubstituted         monovalent non-aromatic condensed heteropolycyclic group,         —N(Q₁)(Q₂), and —B(Q₃)(Q₄),     -   provided that at least one selected from R₁₁ to R₁₄ in Formula         2A is not a hydrogen,     -   b1 in Formula 2A is selected from 1, 2, 3, and 4, and     -   b2 is selected from 0, 1, 2, and 3,     -   each of * and *′ in Formula 2A indicates a binding site to M in         Formula 1, and     -   at least one of substituents of the substituted C₁-C₆₀ alkyl         group, substituted C₂-C₆₀ alkenyl group, substituted C₂-C₆₀         alkynyl group, substituted C₁-C₆₀ alkoxy group, substituted         C₃-C₁₀ cycloalkyl group, substituted C₁-C₁₀ heterocycloalkyl         group, substituted C₃-C₁₀ cycloalkenyl group, substituted C₁-C₁₀         heterocycloalkenyl group, substituted C₆-C₆₀ aryl group,         substituted C₆-C₆₀ aryloxy group, substituted C₆-C₆₀ arylthio         group, substituted C₁-C₆₀ heteroaryl group, substituted         monovalent non-aromatic condensed polycyclic group and         substituted monovalent non-aromatic condensed heteropolycyclic         group may be selected from:     -   a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H,         —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino         group, an amidino group, a hydrazine group, a hydrazone group, a         carboxylic acid group or a salt thereof, a sulfonic acid group         or a salt thereof, a phosphoric acid group or a salt thereof, a         C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl         group, and a C₁-C₆₀ alkoxy group;     -   a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl         group, and a C₁-C₆₀ alkoxy group, each substituted with at least         one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,         —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a         nitro group, an amino group, an amidino group, a hydrazine         group, a hydrazone group, a carboxylic acid group or a salt         thereof, a sulfonic acid group or a salt thereof, a phosphoric         acid group or a salt thereof, a C₃-C₁₀ cycloalkyl group, a         C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a         C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀         aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl         group, a monovalent non-aromatic condensed polycyclic group, a         monovalent non-aromatic condensed heteropolycyclic group,         —N(Q₁₁)(Q₁₂), and —B(Q₁₃)(Q₁₄);     -   a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a         C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a         C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio         group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic         condensed polycyclic group, and a monovalent non-aromatic         condensed heteropolycyclic group;     -   a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a         C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a         C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio         group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic         condensed polycyclic group, and a monovalent non-aromatic         condensed heteropolycyclic group, each substituted with at least         one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,         —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a         nitro group, an amino group, an amidino group, a hydrazine         group, a hydrazone group, a carboxylic acid group or a salt         thereof, a sulfonic acid group or a salt thereof, a phosphoric         acid group or a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀         alkenyl group, a C₂-C₆₀ alkynyl group, a C₁-C₆₀ alkoxy group, a         C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a         C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a         C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio         group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic         condensed polycyclic group, a monovalent non-aromatic condensed         heteropolycyclic group, —N(Q₂₁)(Q₂₂), and —B(Q₂₃)(Q₂₄); and     -   —N(Q₃₁)(Q₃₂) and —B(Q₃₃)(Q₃₄),     -   wherein Q₁ to Q₄, Q₁₁ to Q₁₄, Q₂₁ to Q₂₄, and Q₃₁ to Q₃₄ are         each independently selected from a hydrogen, a deuterium, —F,         —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an         amino group, an amidino group, a hydrazine group, a hydrazone         group, a carboxylic acid group or a salt thereof, a sulfonic         acid group or a salt thereof, a phosphoric acid group or a salt         thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a         substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted         or unsubstituted C₂-C₆₀ alkynyl group, a substituted or         unsubstituted C₁-C₆₀ alkoxy group, a substituted or         unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or         unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or         unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or         unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or         unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted         C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀         arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl         group, a substituted or unsubstituted monovalent non-aromatic         condensed polycyclic group, and a substituted or unsubstituted         monovalent non-aromatic condensed heteropolycyclic group.

Another aspect provides an organic light-emitting device including:

-   -   a first electrode;     -   a second electrode; and     -   an organic layer disposed between the first electrode and the         second electrode,     -   wherein the organic layer includes an emission layer and at         least one organometallic compound represented by Formula 1.

The emission layer may include the organometallic compound.

The organometallic compound included in the emission layer may act as a dopant, and the emission layer may further include a host.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings in which: FIG. 1 is a schematic view of an organic light-emitting device according to an embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present exemplary embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the exemplary embodiments are merely described below, by referring to the figures, to explain aspects of the present disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

It will be understood that when an element is referred to as being “on” another element, it can be directly in contact with the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.

It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the present embodiments.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

About” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” can mean within one or more standard deviations, or within ±30%, 20%, 10%, 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims.

An organometallic compound according to an exemplary embodiment is represented by Formula 1: M(L₁)_(n1)(L₂)_(n2).  Formula 1

M in Formula 1 may be selected from iridium (Ir), platinum (Pt), osmium (Os), titanium (Ti), zirconium (Zr), hafnium (Hf), europium (Eu), terbium (Tb), thulium (Tm), and rhodium (Rh),

For example, M in Formula 1 may be selected from iridium, platinum, osmium, and rhodium.

In an embodiment, M in Formula 1 may be selected from iridium and platinum, but is not limited thereto.

L₁ in Formula 1 is selected from ligands represented by Formula 2A. n1 in Formula 1 indicates the number of groups L₁, and n1 may be 1, 2, or 3. When n1 is 2 or greater, two or more groups L₁ may be identical to or different from each other.

L₂ in Formula 1 may be selected from a monovalent organic ligand, a divalent organic ligand, a trivalent organic ligand, and a tetravalent organic ligand, n2 may be 0, 1, 2, 3, or 4, when n2 is 2 or greater, two or more groups L₂ may be identical to or different from each other.

L₁ and L₂ in Formula 1 may be different from each other.

For example, n1 in Formula 1 may be 1, but is not limited thereto.

In some embodiments, the organometallic compound represented by Formula 1 is not in the form of a salt consisting of an ionic pair, and may be neutral.

In an embodiment, regarding Formula 1, M may be Ir and the sum of n1 and n2 may be 3; or M may be Pt and the sum of n1 and n2 may be 2, and the organometallic compound represented by Formula 1 may not be in the form of a salt consisting of an ionic pair, and may be neutral.

R₁, R₂, and R₁₁ to R₁₅ in Formula 2A may be each independently selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, —SF₅, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted or unsubstituted C₂-C₆₀ alkynyl group, a substituted or unsubstituted C₁-C₆₀ alkoxy group, a substituted or unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀ arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q₁)(Q₂), and —B(Q₃)(Q₄), provided that at least one selected from R₁₁ to R₁₄ in Formula 2A may not be a hydrogen.

For example, R₁ and R₂ in Formula 2A may be each independently selected from

-   -   a C₁-C₁₀ alkyl group, a cyclopentyl group, a cyclohexyl group, a         cycloheptyl group, a cyclooctyl group, an adamantanyl         (adamantyl) group, a norbornanyl (norbornyl) group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a fluorenyl group, a         phenanthrenyl group, an anthracenyl group, a fluoranthenyl         group, a triphenylenyl group, a pyrenyl group, a chrysenyl         group, a pyrrolyl group, a thiophenyl group, a furanyl group, an         imidazolyl group, a pyrazolyl group, a thiazolyl group, an         isothiazolyl group, an oxazolyl group, an isoxazolyl group, a         pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a         pyridazinyl group, an isoindolyl group, an indolyl group, an         indazolyl group, a purinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a cinnolinyl group, a carbazolyl         group, a phenanthrolinyl group, a benzoimidazolyl group, a         benzofuranyl group, a benzothiophenyl group, an         isobenzothiazolyl group, a benzoxazolyl group, an         isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an         oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a         dibenzothiophenyl group, a benzocarbazolyl group, a         dibenzocarbazolyl group, an imidazopyridinyl group, an         imidazopyrimidinyl group, and a 1,2,3,4-tetrahydronaphthyl         group; and     -   a C₁-C₁₀ alkyl group, a cyclopentyl group, a cyclohexyl group, a         cycloheptyl group, a cyclooctyl group, an adamantanyl group, a         norbornanyl group, a cyclopentenyl group, a cyclohexenyl group,         a cycloheptenyl group, a phenyl group, a naphthyl group, a         fluorenyl group, a phenanthrenyl group, an anthracenyl group, a         fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a         chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl         group, an imidazolyl group, a pyrazolyl group, a thiazolyl         group, an isothiazolyl group, an oxazolyl group, an isoxazolyl         group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl         group, a pyridazinyl group, an isoindolyl group, an indolyl         group, an indazolyl group, a purinyl group, a quinolinyl group,         an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a cinnolinyl group, a carbazolyl         group, a phenanthrolinyl group, a benzoimidazolyl group, a         benzofuranyl group, a benzothiophenyl group, an         isobenzothiazolyl group, a benzoxazolyl group, an         isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an         oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a         dibenzothiophenyl group, a benzocarbazolyl group, a         dibenzocarbazolyl group, an imidazopyridinyl group, an         imidazopyrimidinyl group, and 1,2,3,4-tetrahydronaphthyl group,         each substituted with at least one selected from a deuterium,         —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a         hydroxyl group, a cyano group, a nitro group, an amino group, an         amidino group, a hydrazine group, a hydrazone group, a         carboxylic acid group or a salt thereof, a sulfonic acid group         or a salt thereof, a phosphoric acid group or a salt thereof, a         C₁-C₂₀ alkyl group, a C_(r) C₂₀ alkoxy group, a cyclopentyl         group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl         group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a fluorenyl group, a         phenanthrenyl group, an anthracenyl group, a fluoranthenyl         group, a triphenylenyl group, a pyrenyl group, a chrysenyl         group, a pyrrolyl group, a thiophenyl group, a furanyl group, an         imidazolyl group, a pyrazolyl group, a thiazolyl group, an         isothiazolyl group, an oxazolyl group, an isoxazolyl group, a         pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a         pyridazinyl group, an isoindolyl group, an indolyl group, an         indazolyl group, a purinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a cinnolinyl group, a carbazolyl         group, a phenanthrolinyl group, a benzoimidazolyl group, a         benzofuranyl group, a benzothiophenyl group, an         isobenzothiazolyl group, a benzoxazolyl group, an         isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an         oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a         dibenzothiophenyl group, a benzocarbazolyl group, a         dibenzocarbazolyl group, an imidazopyridinyl group, and an         imidazopyrimidinyl group.

In an embodiment, R₁ and R₂ in Formula 2A may be each independently selected from

-   -   a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a         fluorenyl group, a phenanthrenyl group, an anthracenyl group, a         fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a         chrysenyl group, a pyridinyl group, a pyrazinyl group, a         pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a carbazolyl group, a         phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl         group, a benzothiophenyl group, an isobenzothiazolyl group, a         benzoxazolyl group, an isobenzoxazolyl group, a triazinyl group,         a dibenzofuranyl group, a dibenzothiophenyl group, a         benzocarbazolyl group, a dibenzocarbazolyl group, an         imidazopyridinyl group, an imidazopyrimidinyl group, and a         1,2,3,4-tetrahydronaphthyl group; and     -   a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a         fluorenyl group, a phenanthrenyl group, an anthracenyl group, a         fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a         chrysenyl group, a pyridinyl group, a pyrazinyl group, a         pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a carbazolyl group, a         phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl         group, a benzothiophenyl group, an isobenzothiazolyl group, a         benzoxazolyl group, an isobenzoxazolyl group, a triazinyl group,         a dibenzofuranyl group, a dibenzothiophenyl group, a         benzocarbazolyl group, a dibenzocarbazolyl group, an         imidazopyridinyl group, an imidazopyrimidinyl group, and a         1,2,3,4-tetrahydronaphthyl group, each substituted with at least         one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,         —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a         nitro group, an amino group, an amidino group, a hydrazine         group, a hydrazone group, a carboxylic acid group or a salt         thereof, a sulfonic acid group or a salt thereof, a phosphoric         acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀         alkoxy group, a phenyl group, a naphthyl group, a fluorenyl         group, a phenanthrenyl group, an anthracenyl group, a         fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a         chrysenyl group, a pyridinyl group, a pyrazinyl group, a         pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a carbazolyl group, a         phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl         group, a benzothiophenyl group, an isobenzothiazolyl group, a         benzoxazolyl group, an isobenzoxazolyl group, a triazinyl group,         a dibenzofuranyl group, a dibenzothiophenyl group, a         benzocarbazolyl group, a dibenzocarbazolyl group, an         imidazopyridinyl group, and an imidazopyrimidinyl group.

In some embodiments, R₁ and R₂ in Formula 2A may be each independently selected from

-   -   a phenyl group, a naphthyl group, a pyridinyl group, a         pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a         quinoxalinyl group, a quinazolinyl group, a carbazolyl group,         and a 1,2,3,4-tetrahydronaphthyl group; and     -   a phenyl group, a naphthyl group, a pyridinyl group, a         pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a         quinoxalinyl group, a quinazolinyl group, a carbazolyl group,         and a 1,2,3,4-tetrahydronaphthyl group, each substituted with at         least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃,         —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano         group, a nitro group, an amino group, an amidino group, a         hydrazine group, a hydrazone group, a carboxylic acid group or a         salt thereof, a sulfonic acid group or a salt thereof, a         phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a         C₁-C₂₀ alkoxy group, a phenyl group, a naphthyl group, a         pyridinyl group, a pyrimidinyl group, a quinolinyl group, an         isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group,         and a carbazolyl group.

For example, R₁ and R₂ in Formula 2A may be identical to or different from each other. In an embodiment, R₁ and R₂ in Formula 2A may be identical to each other.

In an embodiment, R₁ and R₂ in Formula 2A may be identical to each other, R₁ and R₂ may be selected from a phenyl group; and a phenyl group substituted with at least one C₁-C₁₀ alkyl group.

R₁₁ to R₁₅ in Formula 2A may be each independently selected from

-   -   a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a         cyano group, a nitro group, an amino group, an amidino group, a         hydrazine group, a hydrazone group, a carboxylic acid group or a         salt thereof, a sulfonic acid group or a salt thereof, a         phosphoric acid group or a salt thereof, —SF₅, C₁-C₂₀ alkyl         group, and a C₁-C₂₀ alkoxy group;     -   a C₁-C₂₀ alkyl group and a C₁-C₂₀ alkoxy group, each substituted         with at least one selected from a deuterium, —F, —Cl, —Br, —I,         —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a         cyano group, a nitro group, an amino group, an amidino group, a         hydrazine group, a hydrazone group, a carboxylic acid group or a         salt thereof, a sulfonic acid group or a salt thereof, a         phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group, a         cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a pyridinyl group, and         a pyrimidinyl group;     -   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a fluorenyl group, a         phenanthrenyl group, an anthracenyl group, a fluoranthenyl         group, a triphenylenyl group, a pyrenyl group, a chrysenyl         group, a pyrrolyl group, a thiophenyl group, a furanyl group, an         imidazolyl group, a pyrazolyl group, a thiazolyl group, an         isothiazolyl group, an oxazolyl group, an isoxazolyl group, a         pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a         pyridazinyl group, an isoindolyl group, an indolyl group, an         indazolyl group, a purinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a cinnolinyl group, a carbazolyl         group, a phenanthrolinyl group, a benzoimidazolyl group, a         benzofuranyl group, a benzothiophenyl group, an         isobenzothiazolyl group, a benzoxazolyl group, an         isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an         oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a         dibenzothiophenyl group, a benzocarbazolyl group, a         dibenzocarbazolyl group, an imidazopyridinyl group, and an         imidazopyrimidinyl group;     -   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a fluorenyl group, a         phenanthrenyl group, an anthracenyl group, a fluoranthenyl         group, a triphenylenyl group, a pyrenyl group, a chrysenyl         group, a pyrrolyl group, a thiophenyl group, a furanyl group, an         imidazolyl group, a pyrazolyl group, a thiazolyl group, an         isothiazolyl group, an oxazolyl group, an isoxazolyl group, a         pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a         pyridazinyl group, an isoindolyl group, an indolyl group, an         indazolyl group, a purinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a cinnolinyl group, a carbazolyl         group, a phenanthrolinyl group, a benzoimidazolyl group, a         benzofuranyl group, a benzothiophenyl group, an         isobenzothiazolyl group, a benzoxazolyl group, an         isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an         oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a         dibenzothiophenyl group, a benzocarbazolyl group, a         dibenzocarbazolyl group, an imidazopyridinyl group, and an         imidazopyrimidinyl group, each substituted with at least one         selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂,         —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro         group, an amino group, an amidino group, a hydrazine group, a         hydrazone group, a carboxylic acid group or a salt thereof, a         sulfonic acid group or a salt thereof, a phosphoric acid group         or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group,         a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a fluorenyl group, a         phenanthrenyl group, an anthracenyl group, a fluoranthenyl         group, a triphenylenyl group, a pyrenyl group, a chrysenyl         group, a pyrrolyl group, a thiophenyl group, a furanyl group, an         imidazolyl group, a pyrazolyl group, a thiazolyl group, an         isothiazolyl group, an oxazolyl group, an isoxazolyl group, a         pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a         pyridazinyl group, an isoindolyl group, an indolyl group, an         indazolyl group, a purinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a cinnolinyl group, a carbazolyl         group, a phenanthrolinyl group, a benzoimidazolyl group, a         benzofuranyl group, a benzothiophenyl group, an         isobenzothiazolyl group, a benzoxazolyl group, an         isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an         oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a         dibenzothiophenyl group, a benzocarbazolyl group, a         dibenzocarbazolyl group, an imidazopyridinyl group, and an         imidazopyrimidinyl group; and     -   —N(Q₁)(Q₂) and —B(Q₃)(Q₄),     -   wherein Q₁ to Q₄ may be each independently selected from     -   —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂,         —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and         —CD₂CDH₂;     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group, and a naphthyl group; and     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group, and a naphthyl group, each         substituted with at least one selected from a deuterium, a         C₁-C₁₀ alkyl group, and a phenyl group.

For example, R₁₁ to R₁₅ in Formula 2A may be each independently selected from

-   -   a hydrogen, a deuterium, —F, a cyano group, a nitro group, —SF₅,         a methyl group, an ethyl group, an n-propyl group, an isopropyl         group, an n-butyl group, an isobutyl group, a sec-butyl group, a         tert-butyl group, an n-pentyl group, an isopentyl group, a         sec-pentyl group, a tert-pentyl group, an n-hexyl group, an         iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an         n-heptyl group, an iso-heptyl group, a sec-heptyl group, a         tert-heptyl group, an n-octyl group, an iso-octyl group, a         sec-octyl group, a tert-octyl group, an n-nonyl group, an         iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an         n-decyl group, an iso-decyl group, a sec-decyl group, a         tert-decyl group, a methoxy group, an ethoxy group, a propoxy         group, butoxy group, a pentoxy group, a cyclopentyl group, a         cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an         adamantanyl group, a norbornanyl group, a cyclopentenyl group, a         cyclohexenyl group, a cycloheptenyl group, a phenyl group, a         naphthyl group, a pyridinyl group, and a pyrimidinyl group;     -   a methyl group, an ethyl group, an n-propyl group, an isopropyl         group, an n-butyl group, an isobutyl group, a sec-butyl group, a         tert-butyl group, an n-pentyl group, an isopentyl group, a         sec-pentyl group, a tert-pentyl group, an n-hexyl group, an         iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an         n-heptyl group, an iso-heptyl group, a sec-heptyl group, a         tert-heptyl group, an n-octyl group, an iso-octyl group, a         sec-octyl group, a tert-octyl group, an n-nonyl group, an         iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an         n-decyl group, an iso-decyl group, a sec-decyl group, a         tert-decyl group, a methoxy group, an ethoxy group, a propoxy         group, butoxy group, a pentoxy group, a cyclopentyl group, a         cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an         adamantanyl group, a norbornanyl group, a cyclopentenyl group, a         cyclohexenyl group, a cycloheptenyl group, a phenyl group, a         naphthyl group, a pyridinyl group, and a pyrimidinyl group, each         substituted with at least one selected from a deuterium, —F,         —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a cyano group, a nitro         group, a C₁-C₁₀ alkyl group, a C₁-C₁₀ alkoxy group, a         cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a pyridinyl group, and         a pyrimidinyl group; and     -   —N(Q₁)(Q₂) and —B(Q₃)(Q₄),     -   wherein Q₁ to Q₄ may be each independently selected from     -   —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂,         —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and         —CD₂CDH₂;     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group and a naphthyl group; and     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group, and a naphthyl group, each         substituted with at least one selected from a deuterium, a         C₁-C₁₀ alkyl group, and a phenyl group.

In an embodiment, R₁₁ to R₁₅ in Formula 2A may be each independently selected from a hydrogen, a deuterium, —F, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, groups represented by Formulae 9-1 to 9-17, and groups represented by Formulae 10-1 to 10-28,

-   -   R₁ and R₂ in Formula 2A may be each independently selected from     -   a phenyl group, a naphthyl group, a pyridinyl group, a         pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a         quinoxalinyl group, a quinazolinyl group, and a carbazolyl         group; and     -   a phenyl group, a naphthyl group, a pyridinyl group, a         pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a         quinoxalinyl group, a quinazolinyl group, and a carbazolyl         group, each substituted with at least one selected from a         deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H,         —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino         group, an amidino group, a hydrazine group, a hydrazone group, a         carboxylic acid group or a salt thereof, a sulfonic acid group         or a salt thereof, a phosphoric acid group or a salt thereof, a         C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a         naphthyl group, a pyridinyl group, a pyrimidinyl group, a         quinolinyl group, an isoquinolinyl group, a quinoxalinyl group,         a quinazolinyl group, and a carbazolyl group, but are not         limited thereto:

In Formula 2A, b1 may be selected from 1, 2, 3, and 4, and b2 may be selected from 0, 1, 2, and 3.

For example, b1 in Formula 2A may be 1 or 2, for example, b1 in Formula 2A may be 1, but is not limited thereto.

Each of * and *′ in Formula 2A indicates a binding site to M in Formula 1.

In an embodiment, L₁ in Formula 1 may be selected from ligands represented by Formulae 2A-1 to 2A-15:

Descriptions of R₁, R₂, R₁₁ to R₁₅, b1 and b2 in Formulae 2A-1 to 2A-15 are the same as above, provided that each of R₁₁ to R₁₄ is not hydrogen.

For example, R₁₁ to R₁₄ in Formulae 2A-1 to 2A-15 may be each independently selected from

-   -   a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group,         a nitro group, an amino group, an amidino group, a hydrazine         group, a hydrazone group, a carboxylic acid group or a salt         thereof, a sulfonic acid group or a salt thereof, a phosphoric         acid group or a salt thereof, —SF₅, C₁-C₂₀ alkyl group, and a         C₁-C₂₀ alkoxy group;     -   a C₁-C₂₀ alkyl group and a C₁-C₂₀ alkoxy group, each substituted         with at least one selected from a deuterium, —F, —Cl, —Br, —I,         —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a         cyano group, a nitro group, an amino group, an amidino group, a         hydrazine group, a hydrazone group, a carboxylic acid group or a         salt thereof, a sulfonic acid group or a salt thereof, a         phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group, a         cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a pyridinyl group, and         a pyrimidinyl group;     -   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a fluorenyl group, a         phenanthrenyl group, an anthracenyl group, a fluoranthenyl         group, a triphenylenyl group, a pyrenyl group, a chrysenyl         group, a pyrrolyl group, a thiophenyl group, a furanyl group, an         imidazolyl group, a pyrazolyl group, a thiazolyl group, an         isothiazolyl group, an oxazolyl group, an isoxazolyl group, a         pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a         pyridazinyl group, an isoindolyl group, an indolyl group, an         indazolyl group, a purinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a cinnolinyl group, a carbazolyl         group, a phenanthrolinyl group, a benzoimidazolyl group, a         benzofuranyl group, a benzothiophenyl group, an         isobenzothiazolyl group, a benzoxazolyl group, an         isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an         oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a         dibenzothiophenyl group, a benzocarbazolyl group, a         dibenzocarbazolyl group, an imidazopyridinyl group, and an         imidazopyrimidinyl group;     -   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a fluorenyl group, a         phenanthrenyl group, an anthracenyl group, a fluoranthenyl         group, a triphenylenyl group, a pyrenyl group, a chrysenyl         group, a pyrrolyl group, a thiophenyl group, a furanyl group, an         imidazolyl group, a pyrazolyl group, a thiazolyl group, an         isothiazolyl group, an oxazolyl group, an isoxazolyl group, a         pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a         pyridazinyl group, an isoindolyl group, an indolyl group, an         indazolyl group, a purinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a cinnolinyl group, a carbazolyl         group, a phenanthrolinyl group, a benzoimidazolyl group, a         benzofuranyl group, a benzothiophenyl group, an         isobenzothiazolyl group, a benzoxazolyl group, an         isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an         oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a         dibenzothiophenyl group, a benzocarbazolyl group, a         dibenzocarbazolyl group, an imidazopyridinyl group, and an         imidazopyrimidinyl group, each substituted with at least one         selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂,         —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro         group, an amino group, an amidino group, a hydrazine group, a         hydrazone group, a carboxylic acid group or a salt thereof, a         sulfonic acid group or a salt thereof, a phosphoric acid group         or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group,         a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a fluorenyl group, a         phenanthrenyl group, an anthracenyl group, a fluoranthenyl         group, a triphenylenyl group, a pyrenyl group, a chrysenyl         group, a pyrrolyl group, a thiophenyl group, a furanyl group, an         imidazolyl group, a pyrazolyl group, a thiazolyl group, an         isothiazolyl group, an oxazolyl group, an isoxazolyl group, a         pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a         pyridazinyl group, an isoindolyl group, an indolyl group, an         indazolyl group, a purinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a cinnolinyl group, a carbazolyl         group, a phenanthrolinyl group, a benzoimidazolyl group, a         benzofuranyl group, a benzothiophenyl group, an         isobenzothiazolyl group, a benzoxazolyl group, an         isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an         oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a         dibenzothiophenyl group, a benzocarbazolyl group, a         dibenzocarbazolyl group, an imidazopyridinyl group, and an         imidazopyrimidinyl group; and     -   —N(Q₁)(Q₂) and —B(Q₃)(Q₄),     -   wherein Q₁ to Q₄ are each independently selected from     -   —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂,         —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and         —CD₂CDH₂;     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group, and a naphthyl group; and     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group, and a naphthyl group, each         substituted with at least one selected from a deuterium, a         C₁-C₁₀ alkyl group, and a phenyl group.

In some embodiments, L₁ in Formula 1 may be selected from groups represented by Formula 2A(1):

Descriptions of R₁, R₂ and R₁₁ to R₁₄ in Formula 2A(1) are the same as described above, and descriptions of R_(15a), R_(15b), and R_(15c) are the same as those provided in connection with R₁₅.

For example, L₁ in Formula 1 may be selected from ligands represented by Formulae 2A(1)-1 to 2A(1)-15:

Descriptions of R₁, R₂ and R₁₁ to R₁₄ in Formulae 2A(1)-1 to 2A(1)-15 are the same as described above, provided that each of R₁₁ to R₁₄ is not hydrogen, and descriptions of R_(15a), R_(15b), and R_(15c) are the same as those provided in connection with R₁₅.

For example, in Formulae 2A(1)-1 to 2A(1)-15,

-   -   R₁₁ to R₁₄ may be each independently selected from     -   a deuterium, —F, a cyano group, a nitro group, —SF₅, a methyl         group, an ethyl group, an n-propyl group, an isopropyl group, an         n-butyl group, an isobutyl group, a sec-butyl group, a         tert-butyl group, an n-pentyl group, an isopentyl group, a         sec-pentyl group, a tert-pentyl group, an n-hexyl group, an         iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an         n-heptyl group, an iso-heptyl group, a sec-heptyl group, a         tert-heptyl group, an n-octyl group, an iso-octyl group, a         sec-octyl group, a tert-octyl group, an n-nonyl group, an         iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an         n-decyl group, an iso-decyl group, a sec-decyl group, a         tert-decyl group, a methoxy group, an ethoxy group, a propoxy         group, butoxy group, a pentoxy group, a cyclopentyl group, a         cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an         adamantanyl group, a norbornanyl group, a cyclopentenyl group, a         cyclohexenyl group, a cycloheptenyl group, a phenyl group, a         naphthyl group, a pyridinyl group, and a pyrimidinyl group;     -   a methyl group, an ethyl group, an n-propyl group, an isopropyl         group, an n-butyl group, an isobutyl group, a sec-butyl group, a         tert-butyl group, an n-pentyl group, an isopentyl group, a         sec-pentyl group, a tert-pentyl group, an n-hexyl group, an         iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an         n-heptyl group, an iso-heptyl group, a sec-heptyl group, a         tert-heptyl group, an n-octyl group, an iso-octyl group, a         sec-octyl group, a tert-octyl group, an n-nonyl group, an         iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an         n-decyl group, an iso-decyl group, a sec-decyl group, a         tert-decyl group, a methoxy group, an ethoxy group, a propoxy         group, butoxy group, a pentoxy group, a cyclopentyl group, a         cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an         adamantanyl group, a norbornanyl group, a cyclopentenyl group, a         cyclohexenyl group, a cycloheptenyl group, a phenyl group, a         naphthyl group, a pyridinyl group, and a pyrimidinyl group, each         substituted with at least one selected from a deuterium, —F,         —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a cyano group, a nitro         group, a C₁-C₁₀ alkyl group, a C₁-C₁₀ alkoxy group, a         cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a pyridinyl group, and         a pyrimidinyl group; and     -   —N(Q₁)(Q₂) and —B(Q₃)(Q₄),     -   R_(15a), R_(15b), and R_(15c) may be each independently selected         from     -   a hydrogen, a deuterium, —F, a cyano group, a nitro group, —SF₅,         a methyl group, an ethyl group, an n-propyl group, an isopropyl         group, an n-butyl group, an isobutyl group, a sec-butyl group, a         tert-butyl group, an n-pentyl group, an isopentyl group, a         sec-pentyl group, a tert-pentyl group, an n-hexyl group, an         iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an         n-heptyl group, an iso-heptyl group, a sec-heptyl group, a         tert-heptyl group, an n-octyl group, an iso-octyl group, a         sec-octyl group, a tert-octyl group, an n-nonyl group, an         iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an         n-decyl group, an iso-decyl group, a sec-decyl group, a         tert-decyl group, a methoxy group, an ethoxy group, a propoxy         group, butoxy group, a pentoxy group, a cyclopentyl group, a         cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an         adamantanyl group, a norbornanyl group, a cyclopentenyl group, a         cyclohexenyl group, a cycloheptenyl group, a phenyl group, a         naphthyl group, a pyridinyl group, and a pyrimidinyl group;     -   a methyl group, an ethyl group, an n-propyl group, an isopropyl         group, an n-butyl group, an isobutyl group, a sec-butyl group, a         tert-butyl group, an n-pentyl group, an isopentyl group, a         sec-pentyl group, a tert-pentyl group, an n-hexyl group, an         iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an         n-heptyl group, an iso-heptyl group, a sec-heptyl group, a         tert-heptyl group, an n-octyl group, an iso-octyl group, a         sec-octyl group, a tert-octyl group, an n-nonyl group, an         iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an         n-decyl group, an iso-decyl group, a sec-decyl group, a         tert-decyl group, a methoxy group, an ethoxy group, a propoxy         group, butoxy group, a pentoxy group, a cyclopentyl group, a         cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an         adamantanyl group, a norbornanyl group, a cyclopentenyl group, a         cyclohexenyl group, a cycloheptenyl group, a phenyl group, a         naphthyl group, a pyridinyl group, and a pyrimidinyl group, each         substituted with at least one selected from a deuterium, —F,         —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a cyano group, a nitro         group, a C₁-C₁₀ alkyl group, a C₁-C₁₀ alkoxy group, a         cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a pyridinyl group, and         a pyrimidinyl group; and     -   —N(Q₁)(Q₂) and —B(Q₃)(Q₄),     -   R₁ and R₂ may be each independently selected from     -   a phenyl group, a naphthyl group, a pyridinyl group, a         pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a         quinoxalinyl group, a quinazolinyl group, and a carbazolyl         group; and     -   a phenyl group, a naphthyl group, a pyridinyl group, a         pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a         quinoxalinyl group, a quinazolinyl group, and a carbazolyl         group, each substituted with at least one selected from a         deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H,         —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino         group, an amidino group, a hydrazine group, a hydrazone group, a         carboxylic acid group or a salt thereof, a sulfonic acid group         or a salt thereof, a phosphoric acid group or a salt thereof, a         C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a         naphthyl group, a pyridinyl group, a pyrimidinyl group, a         quinolinyl group, an isoquinolinyl group, a quinoxalinyl group,         a quinazolinyl group, and a carbazolyl group, and     -   Q₁ to Q₄ may be each independently selected from     -   —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂,         —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and         —CD₂CDH₂;     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group, and a naphthyl group; and     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group, and a naphthyl group, each         substituted with at least one selected from a deuterium, a         C₁-C₁₀ alkyl group, and a phenyl group.

In some embodiments, in Formulae 2A(1)-1 to 2A(1)-15,

-   -   R₁₁ to R₁₄ may be each independently selected from a deuterium,         —F, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H,         —CDH₂, —CF₃, —CF₂H, —CFH₂, groups represented by Formulae 9-1 to         9-17, and groups represented by Formulae 10-1 to 10-28,     -   R_(15a), R_(15b), and R_(15c) may be each independently selected         from a hydrogen, a deuterium, —F, a cyano group, a nitro group,         —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, groups         represented by Formulae 9-1 to 9-17, and groups represented by         Formulae 10-1 to 10-28,     -   R₁ and R₂ may be each independently selected from     -   a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a         pyridinyl group, a pyrimidinyl group, a quinolinyl group, an         isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group,         and a carbazolyl group; and     -   a phenyl group, a naphthyl group, a pyridinyl group, a         pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a         quinoxalinyl group, a quinazolinyl group, and a carbazolyl         group, each substituted with at least one selected from a         deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H,         —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino         group, an amidino group, a hydrazine group, a hydrazone group, a         carboxylic acid group or a salt thereof, a sulfonic acid group         or a salt thereof, a phosphoric acid group or a salt thereof, a         C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a         naphthyl group, a pyridinyl group, a pyrimidinyl group, a         quinolinyl group, an isoquinolinyl group, a quinoxalinyl group,         a quinazolinyl group, and a carbazolyl group, but are not         limited thereto.

L₂ in Formula 1 may be selected from groups represented by Formulae 3A to 3G:

In Formulae 3A to 3G,

-   -   Y₁₁ to Y₁₆ may be each independently a carbon (C) or a nitrogen         (N), Y₁₁ and Y₁₂ may be linked to each other via a single bond         or a double bond, Y₁₃ and Y₁₄ may be linked to each other via a         single bond or a double bond, Y₁₅ and Y₁₆ may be linked to each         other via a single bond or a double bond,     -   CY₃ to CY₅ may be each independently selected from a C₅-C₆₀         cyclic group and a C₂-C₆₀ heterocyclic group,     -   a1 to a3 may be each independently an integer of 1 to 5;     -   A₁ is P or As;     -   X_(11a), X_(11b), X_(12a), X_(12b), X_(13a), and X_(13b) may be         each independently selected from N, O, N(R₃₄), P(R₃₅)(R₃₆), and         As(R₃₇)(R₃₈) (provided that X_(12a), X_(12b), X_(13a), and         X_(13b) are neither N nor O);     -   R_(33″) and R_(34″) may be each independently selected from a         single bond, a double bond, a substituted or unsubstituted C₁-C₅         alkylene group, a substituted or unsubstituted C₂-C₅ alkenylene         group, and a substituted or unsubstituted C₆-C₁₀ arylene group;     -   Z₁ to Z₃, R₃₁, R_(32a), R_(32b), R_(32c), R_(33a), R_(33b), R₃₄         to R₃₈, R_(35a), R_(35b), R_(35c), and R_(35d) may be each         independently selected from a hydrogen, a deuterium, —F, —Cl,         —Br, —I, a hydroxyl group, a cyano group, a nitro group, an         amino group, an amidino group, a hydrazine group, a hydrazone         group, a carboxylic acid group or a salt thereof, a sulfonic         acid group or a salt thereof, a phosphoric acid group or a salt         thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a         substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted         or unsubstituted C₂-C₆₀ alkynyl group, a substituted or         unsubstituted C₁-C₆₀ alkoxy group, a substituted or         unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or         unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or         unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or         unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or         unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted         C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀         arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl         group, a substituted or unsubstituted monovalent non-aromatic         condensed polycyclic group, a substituted or unsubstituted         monovalent non-aromatic condensed heteropolycyclic group,         —N(Q₁)(Q₂), —B(Q₃)(Q₄), —Si(Q₅)(Q₆)(Q₇), and —P(═O)(Q₈)(Q₉),     -   each of * and *′ indicates a binding site to M in Formula 1, and     -   at least one of substituents of the substituted C₁-C₅ alkylene         group, substituted C₂-C₅ alkenylene group, substituted C₆-C₁₀         arylene group, substituted C₁-C₆₀ alkyl group, substituted         C₂-C₆₀ alkenyl group, substituted C₂-C₆₀ alkynyl group,         substituted C₁-C₆₀ alkoxy group, substituted C₃-C₁₀ cycloalkyl         group, substituted C₁-C₁₀ heterocycloalkyl group, substituted         C₃-C₁₀ cycloalkenyl group, substituted C₁-C₁₀ heterocycloalkenyl         group, substituted C₆-C₆₀ aryl group, substituted C₆-C₆₀ aryloxy         group, substituted C₆-C₆₀ arylthio group, substituted C₁-C₆₀         heteroaryl group, substituted monovalent non-aromatic condensed         polycyclic group and substituted monovalent non-aromatic         condensed heteropolycyclic group may be selected from     -   a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H,         —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino         group, an amidino group, a hydrazine group, a hydrazone group, a         carboxylic acid group or a salt thereof, a sulfonic acid group         or a salt thereof, a phosphoric acid group or a salt thereof, a         C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl         group, and a C₁-C₆₀ alkoxy group;     -   a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl         group, and a C₁-C₆₀ alkoxy group, each substituted with at least         one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,         —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a         nitro group, an amino group, an amidino group, a hydrazine         group, a hydrazone group, a carboxylic acid group or a salt         thereof, a sulfonic acid group or a salt thereof, a phosphoric         acid group or a salt thereof, a C₃-C₁₀ cycloalkyl group, a         C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a         C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀         aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl         group, a monovalent non-aromatic condensed polycyclic group, a         monovalent non-aromatic condensed heteropolycyclic group,         —N(Q₁₁)(Q₁₂), —B(Q₁₃)(Q₁₄), —Si(Q₁₅)(Q₁₆)(Q₁₇), and         —P(═O)(Q₁₈)(Q₁₉);     -   a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a         C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a         C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio         group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic         condensed polycyclic group, and a monovalent non-aromatic         condensed heteropolycyclic group;     -   a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a         C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a         C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio         group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic         condensed polycyclic group, and a monovalent non-aromatic         condensed heteropolycyclic group, each substituted with at least         one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,         —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a         nitro group, an amino group, an amidino group, a hydrazine         group, a hydrazone group, a carboxylic acid group or a salt         thereof, a sulfonic acid group or a salt thereof, a phosphoric         acid group or a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀         alkenyl group, a C₂-C₆₀ alkynyl group, a C₁-C₆₀ alkoxy group, a         C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a         C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a         C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio         group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic         condensed polycyclic group, a monovalent non-aromatic condensed         heteropolycyclic group, —N(Q₂₁)(Q₂₂), —B(Q₂₃)(Q₂₄),         —Si(Q₂₅)(Q₂₆)(Q₂₇), and —P(═O)(Q₂₈)(Q₂₉); and     -   —N(Q₃₁)(Q₃₂), —B(Q₃₃)(Q₃₄), —Si(Q₃₅)(Q₃₆)(Q₃₇), and         —P(═O)(Q₃₈)(Q₃₉);     -   wherein Q₁ to Q₉, Q₁₁ to Q₁₉, Q₂₁ to Q₂₉ and Q₃₁ to Q₃₉ may be         each independently selected from a hydrogen, a deuterium, —F,         —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an         amino group, an amidino group, a hydrazine group, a hydrazone         group, a carboxylic acid group or a salt thereof, a sulfonic         acid group or a salt thereof, a phosphoric acid group or a salt         thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a         substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted         or unsubstituted C₂-C₆₀ alkynyl group, a substituted or         unsubstituted C₁-C₆₀ alkoxy group, a substituted or         unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or         unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or         unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or         unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or         unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted         C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀         arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl         group, a substituted or unsubstituted monovalent non-aromatic         condensed polycyclic group, and a substituted or unsubstituted         monovalent non-aromatic condensed heteropolycyclic group.

For example, L₂ in Formula 1 may be selected from groups represented by Formulae 3-1 to 3-111:

In Formulae 3-1 to 3-111,

-   -   Z₁, Z₂, Z_(1a), Z_(1b), Z_(2a), Z_(2b), Z_(2c), R_(34a),         R_(34b), and R_(34c) may be each independently selected from     -   a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a         cyano group, a nitro group, an amino group, an amidino group, a         hydrazine group, a hydrazone group, a carboxylic acid group or a         salt thereof, a sulfonic acid group or a salt thereof, a         phosphoric acid group or a salt thereof, —SF₅, C₁-C₂₀ alkyl         group, and a C₁-C₂₀ alkoxy group;     -   a C₁-C₂₀ alkyl group and a C₁-C₂₀ alkoxy group, each substituted         with at least one selected from a deuterium, —F, —Cl, —Br, —I,         —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a         cyano group, a nitro group, an amino group, an amidino group, a         hydrazine group, a hydrazone group, a carboxylic acid group or a         salt thereof, a sulfonic acid group or a salt thereof, a         phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group, a         cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a pyridinyl group, and         a pyrimidinyl group;     -   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a fluorenyl group, a         phenanthrenyl group, an anthracenyl group, a fluoranthenyl         group, a triphenylenyl group, a pyrenyl group, a chrysenyl         group, a pyrrolyl group, a thiophenyl group, a furanyl group, an         imidazolyl group, a pyrazolyl group, a thiazolyl group, an         isothiazolyl group, an oxazolyl group, an isoxazolyl group, a         pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a         pyridazinyl group, an isoindolyl group, an indolyl group, an         indazolyl group, a purinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a cinnolinyl group, a carbazolyl         group, a phenanthrolinyl group, a benzoimidazolyl group, a         benzofuranyl group, a benzothiophenyl group, an         isobenzothiazolyl group, a benzoxazolyl group, an         isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an         oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a         dibenzothiophenyl group, a benzocarbazolyl group, a         dibenzocarbazolyl group, an imidazopyridinyl group, and an         imidazopyrimidinyl group; and     -   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a fluorenyl group, a         phenanthrenyl group, an anthracenyl group, a fluoranthenyl         group, a triphenylenyl group, a pyrenyl group, a chrysenyl         group, a pyrrolyl group, a thiophenyl group, a furanyl group, an         imidazolyl group, a pyrazolyl group, a thiazolyl group, an         isothiazolyl group, an oxazolyl group, an isoxazolyl group, a         pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a         pyridazinyl group, an isoindolyl group, an indolyl group, an         indazolyl group, a purinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a cinnolinyl group, a carbazolyl         group, a phenanthrolinyl group, a benzoimidazolyl group, a         benzofuranyl group, a benzothiophenyl group, an         isobenzothiazolyl group, a benzoxazolyl group, an         isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an         oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a         dibenzothiophenyl group, a benzocarbazolyl group, a         dibenzocarbazolyl group, an imidazopyridinyl group, and an         imidazopyrimidinyl group, each substituted with at least one         selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂,         —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro         group, an amino group, an amidino group, a hydrazine group, a         hydrazone group, a carboxylic acid group or a salt thereof, a         sulfonic acid group or a salt thereof, a phosphoric acid group         or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group,         a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a         cyclooctyl group, an adamantanyl group, a norbornanyl group, a         cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl         group, a phenyl group, a naphthyl group, a fluorenyl group, a         phenanthrenyl group, an anthracenyl group, a fluoranthenyl         group, a triphenylenyl group, a pyrenyl group, a chrysenyl         group, a pyrrolyl group, a thiophenyl group, a furanyl group, an         imidazolyl group, a pyrazolyl group, a thiazolyl group, an         isothiazolyl group, an oxazolyl group, an isoxazolyl group, a         pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a         pyridazinyl group, an isoindolyl group, an indolyl group, an         indazolyl group, a purinyl group, a quinolinyl group, an         isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl         group, a quinazolinyl group, a cinnolinyl group, a carbazolyl         group, a phenanthrolinyl group, a benzoimidazolyl group, a         benzofuranyl group, a benzothiophenyl group, an         isobenzothiazolyl group, a benzoxazolyl group, an         isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an         oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a         dibenzothiophenyl group, a benzocarbazolyl group, a         dibenzocarbazolyl group, an imidazopyridinyl group, and an         imidazopyrimidinyl group; and     -   —N(Q₁)(Q₂), —B(Q₃)(Q₄), —Si(Q₅)(Q₆)(Q₇) and —P(═O)(Q₈)(Q₉),     -   wherein Q₁ to Q₉ may be each independently selected from     -   —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂,         —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and         —CD₂CDH₂;     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group, and a naphthyl group; and     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group, and a naphthyl group, each         substituted with at least one selected from a deuterium and a         C₁-C₁₀ alkyl group,     -   aa2 and ab2 may be each independently 1 or 2,     -   aa3 and ab3 may be each independently an integer selected from 1         to 3,     -   aa4 and ab4 may be each independently an integer selected from 1         to 4, and     -   each of * and *′ indicates a binding site to M in Formula 1.

In some embodiments, L₂ in Formula 1 may be selected from groups represented by Formulae 3-1(1) to 3-1(59) and 3-111:

In Formulae 3-1(1) to 3-1(59) and 3-111,

-   -   Z₁, Z₂, Z_(1a), Z_(1b), Z_(1c), Z_(1d), Z_(2a), Z_(2b), Z_(2c),         Z_(2d), R_(34a), R_(34b), and R_(34c) may be each independently         selected from a deuterium, —F, a cyano group, a nitro group,         —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂,         —Si(Q₅)(Q₆)(Q₇), groups represented by Formulae 9-1 to 9-17, and         groups represented by Formulae 10-1 to 10-28,     -   Q₅ to Q₇ may be each independently selected from     -   —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂,         —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and         —CD₂CDH₂;     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group, and a naphthyl group; and     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group, and a naphthyl group, each         substituted with at least one selected from a deuterium and a         C₁-C₁₀ alkyl group.

In some embodiments, in Formulae 3-1(1) to 3-1(59) and 3-111,

-   -   Z₁, Z₂, Z_(1a), Z_(1b), Z_(1c), Z_(1d), Z_(2a), Z_(2b), Z_(2c),         and Z_(2d) may be each independently selected from a deuterium,         —F, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H,         —CDH₂, —CF₃, —CF₂H, —CFH₂, —Si(Q₅)(Q₆)(Q₇), groups represented         by Formulae 9-1 to 9-17, and groups represented by Formulae 10-1         to 10-28,     -   Q₅ to Q₇ may be each independently selected from     -   —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂,         —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and         —CD₂CDH₂;     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group, and a naphthyl group; and     -   an n-propyl group, an isopropyl group, an n-butyl group, an         isobutyl group, a sec-butyl group, a tert-butyl group, an         n-pentyl group, an isopentyl group, a sec-pentyl group, a         tert-pentyl group, a phenyl group, and a naphthyl group, each         substituted with at least one selected from a deuterium and a         C₁-C₁₀ alkyl group, but are not limited thereto.

In an embodiment, the organometallic compound may be represented by Formula 1 in which L₁ is selected from ligands represented by Formulae 2A-1 to 2A-15 (for example, ligands represented by Formulae 2A(1)-1 to 2A(1)-15) and L₂ is selected from ligands represented by Formulae 3-1 to 3-111 (for example, a ligand represented by Formulae 3-1(1) to 3-1(59) and 3-111).

In some embodiments, the organometallic compound is not in the form of salt, and may be represented by Formula 1 in which M is Ir and the sum of n1 and n2 is 3; or M is Pt and the sum of n1 and n2 is 2, L₁ is selected from ligands represented by Formulae 2A-1 to 2A-15 (for example, ligands represented by Formulae 2A(1)-1 to 2A(1)-15), and L₂ is selected from ligands represented by Formulae 3-1 to 3-111 (for example, ligands represented by Formulae 3-1(1) to 3-1(59) and 3-111).

For example, the organometallic compound represented by Formula 1 may be one of Compounds 1 to 30, but is not limited thereto:

L₁ in Formula 1 is selected from ligands represented by Formula 2A, and at least one selected from R₁₁ to R₁₄ in Formula 2A is not hydrogen. That is, an embodiment in which all of R₁₁ to R₁₄ in Formula 2A are hydrogen at the same time is excluded. While wishing not to be bound by a theory, it is understood that when R₁₁ to R₁₄ in Formula 2A are simultaneously hydrogen, the organometallic compound represented by Formula 1 has excellent heat-resistance and degradation-resistance, and accordingly, an organic light-emitting device including the organometallic compound may have high efficiency and long lifespan.

In some embodiments, L₁ in Formula 1 may be selected from ligands represented by Formula 2A, and b1 in Formula 2A, which indicates the number of *—P(═O)(R₁)(R₂), may be 1, 2, 3, or 4. That is, a benzene ring in the ligand represented by Formula 2A necessarily has *—P(═O)(R₁)(R₂), which is an electron withdrawing group, as a substituent. Thus, the organometallic compound represented by Formula 1 may have a relatively low highest occupied molecular orbital (HOMO) energy level (that is, a HOMO energy level having a great absolute value), thereby emitting green light that is shifted to a relatively shorter wavelength.

For example, the HOMO, the lowest unoccupied molecular orbital (LUMO), and triplet (T₁) energy level of some of the organometallic compounds were evaluated by using a DFT method of Gaussian program (B3LYP, structurally optimized at the level of 6-31G(d,p)), and evaluation results thereof are shown in Table 1.

TABLE 1 Compound No. HOMO (eV) LUMO (eV) T₁ energy level (eV)  1 −4.996 −1.330 2.650  2 −4.987 −1.323 2.649  3 −5.004 −1.320 2.653  4 −5.016 −1.357 2.649  5 −4.992 −1.329 2.650  6 −4.983 −1.320 2.649  7 −5.024 −1.542 2.547  8 −5.002 −1.601 2.556  9 −4.993 −1.318 2.651 10 −5.007 −1.410 2.613 11 −4.982 −1.414 2.632 12 −4.978 −1.365 2.649 13 −4.957 −1.345 2.598 14 −4.924 −1.287 2.637 15 −4.918 −1.267 2.655 16 −4.919 −1.278 2.636 17 −4.935 −1.320 2.666 18 −4.952 −1.509 2.533 19 −4.943 −1.490 2.534 20 −4.938 −1.511 2.530 21 −4.963 −1.551 2.544 22 −4.978 −1.515 2.537 23 −4.924 −1.287 2.637 24 −4.918 −1.267 2.655 25 −4.919 −1.278 2.636 26 −4.935 −1.320 2.666 27 −4.952 −1.509 2.533 28 −4.943 −1.490 2.534 29 −4.938 −1.511 2.530 30 −4.963 −1.551 2.544 B −4.848 −1.187 2.632 C −4.811 −1.196 2.569 D −4.814 −1.231 2.582 Compound B

Compound C

Compound D

Referring to Table 1, it may be seen that the organometallic compound represented by Formula 1 is suitable for use as a material for an organic light-emitting device.

A method of synthesis of the organometallic compound represented by Formula 1 would be readily recognizable by one of ordinary skill in the art by referring to Synthesis Example.

Accordingly, the organometallic compound represented by Formula 1 is suitable for use as an organic layer of an organic light-emitting device, for example, a dopant for an emission layer in an organic layer. According to another aspect of the present disclosure, provided is an organic light-emitting device including:

-   -   a first electrode;     -   a second electrode; and     -   an organic layer disposed between the first electrode and the         second electrode,     -   wherein the organic layer includes the emission layer, and at         least one organometallic compound represented by Formula 1.

The organic light-emitting device may have, due to the inclusion of the organic layer including the organometallic compound represented by Formula 1, low driving voltage, high efficiency, high power, high quantum efficiency, long lifespan, and excellent color purity.

The organometallic compound represented by Formula 1 may be used between a pair of electrodes of an organic light-emitting device. For example, the organometallic compound represented by Formula 1 may be included in the emission layer. In this regard, the organometallic compound acts as a dopant, and the emission layer may further include a host (that is, an amount of the organometallic compound represented by Formula 1 is smaller than an amount of the host).

The term “organic layer” as used herein refers to a single layer and/or a plurality of layers disposed between the first electrode and the second electrode of an organic light-emitting device. The “organic layer” may include, in addition to an organic compound, an organometallic complex including metal.

FIG. 1 is a schematic view of an organic light-emitting device 10 according to an embodiment. Hereinafter, the structure of an organic light-emitting device according to an embodiment and a method of manufacturing an organic light-emitting device 10 according to an embodiment will be described in connection with FIG. 1. The organic light-emitting device 10 includes a first electrode 11, an organic layer 15, and a second electrode 19, which are sequentially stacked.

In FIG. 1, a substrate may be additionally disposed under the first electrode 11 or above the second electrode 19. For use as the substrate, any substrate that is used in general organic light-emitting devices may be used, and the substrate may be a glass substrate or transparent plastic substrate, each with excellent mechanical strength, thermal stability, transparency, surface smoothness, ease of handling, and water-resistance.

The first electrode 11 may be formed by depositing or sputtering a material for forming the first electrode on the substrate. The first electrode 11 may be an anode. The material for the first electrode 11 may be selected from materials with a high work function to allow holes be easily provided. The first electrode 11 may be a reflective electrode or a transmissive electrode. The material for the first electrode may be, for example, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO₂), and zinc oxide (ZnO). In some embodiments, magnesium (Mg), aluminum (Al), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), or magnesium-silver (Mg—Ag) may be used as the material for the first electrode.

The first electrode 11 may have a single-layer structure or a multi-layer structure including two or more layers. For example, the first electrode 11 may have a three-layered structure of ITO/Ag/ITO, but the structure of the first electrode 110 is not limited thereto.

An organic layer 15 is disposed on the first electrode 11.

The organic layer 15 may include a hole transport region, an emission layer, and an electron transport region.

The hole transport region may be disposed between the first electrode 11 and the emission layer.

The hole transport region may include at least one selected from a hole injection layer, a hole transport layer, an electron blocking layer, and a buffer layer.

The hole transport region may include only either a hole injection layer or a hole transport layer. In some embodiments, the hole transport region may have a structure of hole injection layer/hole transport layer or hole injection layer/hole transport layer/electron blocking layer, which are sequentially stacked in this stated order from the first electrode 11.

A hole injection layer hole injection layer may be formed on the first electrode 11 by using various methods, such as vacuum deposition, spin coating, casting, or Langmuir-Blodgett (LB).

When a hole injection layer is formed by vacuum deposition, the deposition conditions may vary according to a material that is used to form the hole injection layer, and the structure and thermal characteristics of the hole injection layer. For example, the deposition conditions may include a deposition temperature of about 100 to about 500° C., a vacuum pressure of about 10⁻⁸ to about 10⁻³ torr, and a deposition rate of about 0.01 to about 100 Angstroms per second (Å/sec). However, the deposition conditions are not limited thereto.

When the hole injection layer is formed using spin coating, coating conditions may vary according to the material used to form the hole injection layer, and the structure and thermal properties of the hole injection layer. For example, a coating rate may be from about 2,000 revolutions per minute (rpm) to about 5,000 rpm, and a temperature at which a heat treatment is performed to remove a solvent after coating may be from about 80° C. to about 200° C. However, the coating conditions are not limited thereto.

Conditions for a hole transport layer and an electron blocking layer may be understood by referring to conditions for forming the hole injection layer.

The hole transport region may include at least one selected from m-MTDATA, TDATA, 2-TNATA, NPB, β-NPB, TPD, Spiro-TPD, Spiro-NPB, methylated NPB, TAPC, HMTPD, 4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA), polyaniline/dodecylbenzenesulfonic acid (Pani/DBSA), poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS), polyaniline/camphor sulfonic acid (PANI/CSA), (polyaniline)/poly(4-styrenesulfonate) (Pani/PSS), a compound represented by Formula 201 below, and a compound represented by Formula 202 below:

Ar₁₀₁ and Ar₁₀₂ in Formula 201 may be each independently selected from

-   -   a phenylene group, a pentalenylene group, an indenylene group, a         naphthylene group, an azulenylene group, a heptalenylene group,         an acenaphthylene group, a fluorenylene group, a phenalenylene         group, a phenanthrenylene group, an anthracenylene group, a         fluoranthenylene group, a triphenylenylene group, a pyrenylene         group, a chrysenylenylene group, a naphthacenylene group, a         picenylene group, a perylenylene group, and a pentacenylene         group; and     -   a phenylene group, a pentalenylene group, an indenylene group, a         naphthylene group, an azulenylene group, a heptalenylene group,         an acenaphthylene group, a fluorenylene group, a phenalenylene         group, a phenanthrenylene group, an anthracenylene group, a         fluoranthenylene group, a triphenylenylene group, a pyrenylene         group, a chrysenylenylene group, a naphthacenylene group, a         picenylene group, a perylenylene group, and a pentacenylene         group, each substituted with at least one selected from a         deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a         nitro group, an amino group, an amidino group, a hydrazine         group, a hydrazone group, a carboxylic acid group or a salt         thereof, a sulfonic acid or a salt thereof, a phosphoric acid or         a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a         C₂-C₆₀ alkynyl group, a C₁-C₆₀ alkoxy group, a C₃-C₁₀ cycloalkyl         group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkyl         group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a         C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀         heteroaryl group, a monovalent non-aromatic condensed polycyclic         group, and a monovalent non-aromatic condensed heteropolycyclic         group.

In Formula 201, xa and xb may be each independently an integer of 0 to 5, or 0, 1, or 2. For example, xa is 1 and xb may be 0, but xa and xb are not limited thereto.

R₁₀₁ to R₁₀₈, R₁₁₁ to R₁₁₉ and R₁₂₁ to R₁₂₄ in Formulae 201 and 202 may be each independently selected from

-   -   a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a         cyano group, a nitro group, an amino group, an amidino group, a         hydrazine group, a hydrazone group, a carboxylic acid group or a         salt thereof, a sulfonic acid group or a salt thereof, a         phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group         (for example, a methyl group, an ethyl group, a propyl group, a         butyl group, a pentyl group, a hexyl group, and so on), and a         C₁-C₁₀ alkoxy group (for example, a methoxy group, an ethoxy         group, a propoxy group, a butoxy group, a pentoxy group, and so         on);     -   a C₁-C₁₀ alkyl group or a C₁-C₁₀ alkoxy group, each substituted         with at least one selected from a deuterium, —F, —Cl, —Br, —I, a         hydroxyl group, a cyano group, a nitro group, an amino group, an         amidino group, a hydrazine group, a hydrazone group, a         carboxylic acid group or a salt thereof, a sulfonic acid group         or a salt thereof, and a phosphoric acid group or a salt         thereof;     -   a phenyl group, a naphthyl group, an anthracenyl group, a         fluorenyl group, and a pyrenyl group; and     -   a phenyl group, a naphthyl group, an anthracenyl group, a         fluorenyl group, and a pyrenyl group, each substituted with at         least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl         group, a cyano group, a nitro group, an amino group, an amidino         group, a hydrazine group, a hydrazone group, a carboxylic acid         group or a salt thereof, a sulfonic acid group or a salt         thereof, a phosphoric acid group or a salt thereof, a C₁-C₁₀         alkyl group, and a C₁-C₁₀ alkoxy group, but they are not limited         thereto.

R₁₀₉ in Formula 201 may be selected from

-   -   a phenyl group, a naphthyl group, an anthracenyl group and a         pyridinyl group; and     -   a phenyl group, a naphthyl group, an anthracenyl group and a         pyridinyl group, each substituted with at least one selected         from a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano         group, a nitro group, an amino group, an amidino group, a         hydrazine group, a hydrazone group, a carboxylic acid group or a         salt thereof, a sulfonic acid or a salt thereof, a phosphoric         acid or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy         group, a phenyl group, a naphthyl group, an anthracenyl group,         and a pyridinyl group.

According to an embodiment, the compound represented by Formula 201 may be represented by Formula 201A, but is not limited thereto:

-   -   wherein R₁₀₁, R₁₁₁, R₁₁₂, and R₁₀₉ in Formula 201A may be         understood by referring to the description provided herein.

For example, the compound represented by Formula 201, and the compound represented by Formula 202 may include compounds HT1 to HT20 illustrated below, but are not limited thereto.

A thickness of the hole transport region may be in a range of about 100 Angstroms (∪) to about 10,000 ∪, for example, about 100 ═ to about 1,000 ∪. When the hole transport region includes a hole injection layer and a hole transport layer, the thickness of the hole injection layer may be in a range of about 100 Å to about 10,000 Å, and for example, about 100 Å to about 1,000 Å, and the thickness of the hole transport layer may be in a range of about 50 Å to about 2,000 Å, and for example, about 100 Å to about 1,500 Å. While not wishing to be bound by a theory, it is understood that when the thicknesses of the hole transport region, the hole injection layer, and the hole transport layer are within these ranges, satisfactory hole transporting characteristics may be obtained without a substantial increase in driving voltage.

The hole transport region may further include, in addition to these materials, a charge-generation material for the improvement of conductive properties. The charge-generation material may be homogeneously or non-homogeneously dispersed in the hole transport region.

The charge-generation material may be, for example, a p-dopant. The p-dopant may be one selected from a quinone derivative, a metal oxide, and a cyano group-containing compound, but embodiments are not limited thereto. Non-limiting examples of the p-dopant are a quinone derivative, such as tetracyanoquinonedimethane (TCNQ) or 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinonedimethane (F4-TCNQ); a metal oxide, such as a tungsten oxide or a molybdenium oxide; and a cyano group-containing compound, such as Compound HT-D1 below, but are not limited thereto.

The hole transport region may include a buffer layer.

Also, the buffer layer may compensate for an optical resonance distance according to a wavelength of light emitted from the emission layer, and thus, efficiency of a formed organic light-emitting device may be improved.

Then, an emission layer (EML) may be formed on the hole transport region by vacuum deposition, spin coating, casting, LB deposition, or the like. When the emission layer is formed by vacuum deposition or spin coating, the deposition or coating conditions may be similar to those applied to form the hole injection layer although the deposition or coating conditions may vary according to the material that is used to form the emission layer.

Meanwhile, when the hole transport region includes an electron blocking layer, a material for the electron blocking layer may be selected from materials for the hole transport region described above and materials for a host to be explained later. However, the material for the electron blocking layer is not limited thereto. For example, when the hole transport region includes an electron blocking layer, a material for the electron blocking layer may be mCP, which will be explained later.

The emission layer may include a host and a dopant, and the dopant may include the organometallic compound represented by Formula 1.

For example, a HOMO energy level of the host may be in a range of −5.3 electron Volts (eV) to −5.8 eV,

-   -   a LUMO energy level of the host may be in a range of −1.6 eV to         −2.0 eV, and     -   a T₁ energy level of the host may be in a range of 2.7 eV to 2.9         eV.

While not wishing to be bound by a theory, it is understood that in organic light-emitting device including an emission layer that includes a host having such ranges of the HOMO, LUMO, and T₁ energy level and the organometallic compound represented by Formula 1 may have high efficiency, high luminance, and long lifespan obtained by efficient energy transition from the host to the dopant.

The host may include at least one selected form TPBi, TBADN, ADN (also referred to as “DNA”), CBP, CDBP, TCP, mCP, Compound H50, and Compound H51:

In some embodiments, the host may further include a compound represented by Formula 301 below.

Ar₁₁₁ to Ar₁₁₂ in Formula 301 may be each independently selected from

-   -   a phenylene group, a naphthylene group, a phenanthrenylene         group, and a pyrenylene group; and     -   a phenylene group, a naphthylene group, a phenanthrenylene         group, and a pyrenylene group, each substituted with at least         one selected from a phenyl group, a naphthyl group, and an         anthracenyl group.

Ar₁₁₃ to Ar₁₁₆ in Formula 301 may be each independently selected from

-   -   a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a         phenanthrenyl group, and a pyrenyl group; and     -   a phenyl group, a naphthyl group, a phenanthrenyl group, and a         pyrenyl group, each substituted with at least one selected from         a phenyl group, a naphthyl group, and an anthracenyl group.

g, h, l, and j in Formula 301 may be each independently an integer of 0 to 4, for example, an integer of 0, 1, or 2.

Ar₁₁₃ to Ar₁₁₆ in Formula 301 may be each independently selected from

-   -   a C₁-C₁₀ alkyl group substituted with at least one selected from         a phenyl group, a naphthyl group, and an anthracenyl group;     -   a phenyl group, a naphthyl group, an anthracenyl group, a         pyrenyl, a phenanthrenyl group, and a fluorenyl group;     -   a phenyl group, a naphthyl group, an anthracenyl group, a         pyrenyl group, a phenanthrenyl group, and a fluorenyl group,         each substituted with at least one selected from deuterium, —F,         —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an         amino group, an amidino group, a hydrazine group, a hydrazone         group, a carboxylic acid group or a salt thereof, a sulfonic         acid or a salt thereof, a phosphoric acid or a salt thereof, a         C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl         group, a C₁-C₆₀ alkoxy group, a phenyl group, a naphthyl group,         an anthracenyl group, a pyrenyl group, a phenanthrenyl group,         and a fluorenyl group; and

but embodiments are not limited thereto.

In some embodiments, the host may include a compound represented by Formula 302 below:

Ar₁₂₂ to Ar₁₂₅ in Formula 302 are the same as described in detail in connection with Ar₁₁₃ in Formula 301.

Ar₁₂₆ and Ar₁₂₇ in Formula 302 may be each independently a C₁-C₁₀ alkyl group (for example, a methyl group, an ethyl group, or a propyl group).

k and l in Formula 302 may be each independently an integer of 0 to 4. For example, k and l may be 0, 1, or 2.

The compound represented by Formula 301 and the compound represented by Formula 302 may include Compounds H1 to H42 illustrated below, but are not limited thereto.

When the organic light-emitting device is a full color organic light-emitting device, the emission layer may be patterned into a red emission layer, a green emission layer, and a blue emission layer. In some embodiments, due to a stack structure including a red emission layer, a green emission layer, and/or a blue emission layer, the emission layer may emit white light.

When the emission layer includes a host and a dopant, an amount of the dopant may be in a range of about 0.01 to about 15 parts by weight based on 100 parts by weight of the host, but is not limited thereto.

A thickness of the emission layer may be in a range of about 100 Å to about 1,000 Å, for example, about 200 Å to about 600 Å. While not wishing to be bound by a theory, it is understood that when the thickness of the emission layer is within this range, excellent light-emission characteristics may be obtained without a substantial increase in driving voltage.

Then, an electron transport region may be disposed on the emission layer.

The electron transport region may include at least one selected from a hole blocking layer, an electron transport layer, and an electron injection layer.

For example, the electron transport region may have a structure of hole blocking layer/electron transport layer/electron injection layer or a structure of electron transport layer/electron injection layer, but the structure of the electron transport region is not limited thereto. The electron transport layer may have a single-layered structure or a multi-layer structure including two or more different materials.

Conditions for forming the hole blocking layer, the electron transport layer, and the electron injection layer which constitute the electron transport region may be understood by referring to the conditions for forming the hole injection layer.

When the electron transport layer includes a hole blocking layer, the hole blocking layer may include, for example, at least one of BCP, Bphen, and Balq but is not limited thereto.

A thickness of the hole blocking layer may be in a range of about 20 Å to about 1,000 Å, for example, about 30 Å to about 300 Å. While not wishing to be bound by a theory, it is understood that when the thickness of the hole blocking layer is within these ranges, the hole blocking layer may have improved hole blocking ability without a substantial increase in driving voltage.

The electron transport layer may further include at least one selected from BCP, Bphen, Alq₃, Balq, TAZ, and NTAZ.

In some embodiments, the electron transport layer may include at least one of ET1 and ET2, but are not limited thereto:

A thickness of the electron transport layer may be in a range of about 100 Å to about 1,000 Å, for example, about 150 Å to about 500 Å. While not wishing to be bound by a theory, it is understood that when the thickness of the electron transport layer is within the range described above, the electron transport layer may have satisfactory electron transport characteristics without a substantial increase in driving voltage.

Also, the electron transport layer may further include, in addition to the materials described above, a metal-containing material.

The metal-containing material may include a Li complex. The Li complex may include, for example, Compound ET-D1 (lithium quinolate, LiQ) or ET-D2.

The electron transport layer may include an electron injection layer (EIL) that promotes flow of electrons from the second electrode 19 thereinto.

The electron injection layer may include at least one selected from, LiF, NaCl, CsF, Li₂O, BaO, and LiQ.

A thickness of the electron injection layer may be in a range of about 1 Å to about 100 Å, about 3 Å to about 90 Å. While not wishing to be bound by a theory, it is understood that when the thickness of the electron injection layer is within the range described above, the electron injection layer may have satisfactory electron injection characteristics without a substantial increase in driving voltage.

The second electrode 19 is disposed on the organic layer 15. The second electrode 19 may be a cathode. A material for forming the second electrode 19 may be selected from metal, an alloy, an electrically conductive compound, and a combination thereof, which have a relatively low work function. For example, lithium (Li), magnesium (Mg), aluminum (Al), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), or magnesium-silver (Mg—Ag) may be formed as a material for forming the second electrode 19. In some embodiments, to manufacture a top emission type light-emitting device, a transmissive electrode formed using ITO or IZO may be used as the second electrode 19.

Hereinbefore, the organic light-emitting device has been described with reference to FIG. 1, but is not limited thereto.

A C₁-C₆₀ alkyl group as used herein refers to a linear or branched aliphatic hydrocarbon monovalent group having 1 to 60 carbon atoms. Detailed examples thereof are a methyl group, an ethyl group, a propyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an iso-amyl group, and a hexyl group. A C₁-C₆₀ alkylene group as used herein refers to a divalent group having the same structure as the C₁-C₆₀ alkyl group.

A C₁-C₆₀ alkoxy group as used herein refers to a monovalent group represented by —OA₁₀₁ (wherein A₁₀₁ is the C₁-C₆₀ alkyl group). Detailed examples thereof are a methoxy group, an ethoxy group, and an isopropyloxy group.

A C₂-C₆₀ alkenyl group as used herein refers to a hydrocarbon group formed by including at least one carbon double bond in the middle or at the terminal of the C₂-C₆₀ alkyl group. Detailed examples thereof are an ethenyl group, a propenyl group, and a butenyl group. A C₂-C₆₀ alkenylene group as used herein refers to a divalent group having the same structure as the C₂-C₆₀ alkenyl group.

A C₂-C₆₀ alkynyl group as used herein refers to a hydrocarbon group formed by including at least one carbon trip bond in the middle or at the terminal of the C₂-C₆₀ alkyl group. Detailed examples thereof are an ethynyl group, and a propynyl group. A C₂-C₆₀ alkynylene group as used herein refers to a divalent group having the same structure as the C₂-C₆₀ alkynyl group.

A C₃-C₁₀ cycloalkyl group as used herein refers to a monovalent hydrocarbon monocyclic group having 3 to 10 carbon atoms. Detailed examples thereof are a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group. A C₃-C₁₀ cycloalkylene group as used herein refers to a divalent group having the same structure as the C₃-C₁₀ cycloalkyl group.

A C₁-C₁₀ heterocycloalkyl group as used herein refers to a monovalent monocyclic group having at least one hetero atom selected from N, O, P, and S as a ring-forming atom and 1 to 10 carbon atoms. Detailed examples thereof are a tetrahydrofuranyl group, and a tetrahydrothiophenyl group. A C₁-C₁₀ heterocycloalkylene group as used herein refers to a divalent group having the same structure as the C₁-C₁₀ heterocycloalkyl group.

A C₃-C₁₀ cycloalkenyl group as used herein refers to a monovalent monocyclic group that has 3 to 10 carbon atoms and at least one double bond in the ring thereof and which is not aromatic. Detailed examples thereof are a cyclopentenyl group, a cyclohexenyl group, and a cycloheptenyl group. A C₃-C₁₀ cycloalkenylene group as used herein refers to a divalent group having the same structure as the C₃-C₁₀ cycloalkenyl group.

A C₁-C₁₀ heterocycloalkenyl group as used herein refers to a monovalent monocyclic group that has at least one hetero atom selected from N, O, P, and S as a ring-forming atom, 1 to 10 carbon atoms, and at least one double bond in its ring. Detailed examples of the C₁-C₁₀ heterocycloalkenyl group are a 2,3-dihydrofuranyl group and a 2,3-dihydrothiophenyl group. A C₁-C₁₀ heterocycloalkenylene group as used herein refers to a divalent group having the same structure as the C₁-C₁₀ heterocycloalkenyl group.

A C₆-C₆₀ aryl group as used herein refers to a monovalent group having a carbocyclic aromatic system having 6 to 60 carbon atoms, and a C₆-C₆₀ arylene group as used herein refers to a divalent group having a carbocyclic aromatic system having 6 to 60 carbon atoms. Detailed examples of the C₆-C₆₀ aryl group are a phenyl group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a pyrenyl group, and a chrysenyl group. When the C₆-C₆₀ aryl group and the C₆-C₆₀ arylene group each include two or more rings, the rings may be fused to each other.

A C₁-C₆₀ heteroaryl group as used herein refers to a monovalent group having a carbocyclic aromatic system that has at least one hetero atom selected from N, O, P, and S as a ring-forming atom, and 1 to 60 carbon atoms. A C₁-C₆₀ heteroarylene group as used herein refers to a divalent group having a carbocyclic aromatic system that has at least one hetero atom selected from N, O, P, and S as a ring-forming atom, and 1 to 60 carbon atoms. Examples of the C₁-C₆₀ heteroaryl group are a pyridinyl group, a pyrimidinyl group, a pyrazinyl group, a pyridazinyl group, a triazinyl group, a quinolinyl group, and an isoquinolinyl group. When the C₁-C₆₀ heteroaryl group and the C₁-C₆₀ heteroarylene group each include two or more rings, the rings may be fused to each other.

A C₆-C₆₀ aryloxy group as used herein indicates —OA₁₀₂ (wherein A₁₀₂ is the C₆-C₆₀ aryl group), and a C₆-C₆₀ arylthio group as used herein indicates —SA₁₀₃ (wherein A₁₀₃ is the C₆-C₆₀ aryl group).

A monovalent non-aromatic condensed polycyclic group as used herein refers to a monovalent group (for example, having 8 to 60 carbon atoms) that has two or more rings condensed to each other, only carbon atoms as a ring forming atom, and which is non-aromatic in the entire molecular structure. A detailed example of the monovalent non-aromatic condensed polycyclic group is a fluorenyl group. A divalent non-aromatic condensed polycyclic group as used herein refers to a divalent group having the same structure as the monovalent non-aromatic condensed polycyclic group.

A monovalent non-aromatic condensed heteropolycyclic group as used herein refers to a monovalent group (for example, having 2 to 60 carbon atoms) that has two or more rings condensed to each other, has a heteroatom selected from N, O P, and S, other than carbon atoms, as a ring forming atom, and which is non-aromatic in the entire molecular structure. An example of the monovalent non-aromatic condensed heteropolycyclic group is a carbazolyl group. A divalent non-aromatic condensed heteropolycyclic group as used herein refers to a divalent group having the same structure as the monovalent non-aromatic condensed heteropolycyclic group.

At least one of substituents of the substituted C₁-C₆₀ alkyl group, substituted C₂-C₆₀ alkenyl group, substituted C₂-C₆₀ alkynyl group, substituted C₁-C₆₀ alkoxy group, substituted C₃-C₁₀ cycloalkyl group, substituted C₁-C₁₀ heterocycloalkyl group, substituted C₃-C₁₀ cycloalkenyl group, substituted C₁-C₁₀ heterocycloalkenyl group, substituted C₆-C₆₀ aryl group, substituted C₆-C₆₀ aryloxy group, substituted C₆-C₆₀ arylthio group, substituted C₁-C₆₀ heteroaryl group, substituted monovalent non-aromatic condensed polycyclic group, and substituted monovalent non-aromatic condensed heteropolycyclic group used herein is selected from

-   -   a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H,         —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino         group, an amidino group, a hydrazine group, a hydrazone group, a         carboxylic acid group or a salt thereof, a sulfonic acid or a         salt thereof, a phosphoric acid or a salt thereof, a C₁-C₆₀         alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, and         a C₁-C₆₀ alkoxy group;     -   a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl         group, and a C₁-C₆₀ alkoxy group, each substituted with at least         one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,         —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a         nitro group, an amino group, an amidino group, a hydrazine         group, a hydrazone group, a carboxylic acid group or a salt         thereof, a sulfonic acid or a salt thereof, a phosphoric acid or         a salt thereof, a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀         heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀         heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy         group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a         monovalent non-aromatic condensed polycyclic group, a monovalent         non-aromatic condensed heteropolycyclic group, —N(Q₁₁)(Q₁₂),         —B(Q₁₃)(Q₁₄), —Si(Q₁₅)(Q₁₆)(Q₁₇), and —P(═O)(Q₁₈)(Q₁₉);     -   a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a         C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a         C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio         group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic         condensed polycyclic group, and a monovalent non-aromatic         condensed heteropolycyclic group;     -   a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a         C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a         C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio         group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic         condensed polycyclic group, and a monovalent non-aromatic         condensed heteropolycyclic group, each substituted with at least         one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,         —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a         nitro group, an amino group, an amidino group, a hydrazine         group, a hydrazone group, a carboxylic acid group or a salt         thereof, a sulfonic acid or a salt thereof, a phosphoric acid or         a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a         C₂-C₆₀ alkynyl group, a C₁-C₆₀ alkoxy group, a C₃-C₁₀ cycloalkyl         group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl         group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a         C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀         heteroaryl group, a monovalent non-aromatic condensed polycyclic         group, a monovalent non-aromatic condensed heteropolycyclic         group, —N(Q₂₁)(Q₂₂), —B(Q₂₃)(Q₂₄), —Si(Q₂₅)(Q₂₆)(Q₂₇), and         —P(═O)(Q₂₈)(Q₂₉); and     -   —N(Q₃₁)(Q₃₂), —B(Q₃₃)(Q₃₄), —Si(Q₃₅)(Q₃₆)(Q₃₇), and         —P(═O)(Q₃₈)(Q₃₉);     -   wherein Q₁ to Q₉, Q₁₁ to Q₁₉, Q₂₁ to Q₂₉ and Q₃₁ to Q₃₉ may be         each independently selected from a hydrogen, a deuterium, —F,         —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an         amino group, an amidino group, a hydrazine group, a hydrazone         group, a carboxylic acid group or a salt thereof, a sulfonic         acid or a salt thereof, a phosphoric acid or a salt thereof, a         substituted or unsubstituted C₁-C₆₀ alkyl group, a substituted         or unsubstituted C₂-C₆₀ alkenyl group, a substituted or         unsubstituted C₂-C₆₀ alkynyl group, a substituted or         unsubstituted C₁-C₆₀ alkoxy group, a substituted or         unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or         unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or         unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or         unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or         unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted         C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀         arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl         group, a substituted or unsubstituted monovalent non-aromatic         condensed polycyclic group, and a substituted or unsubstituted         monovalent non-aromatic condensed heteropolycyclic group.

Hereinafter, a compound and an organic light-emitting device according to embodiments are described in detail with reference to Synthesis Example and Examples. However, the organic light-emitting device is not limited thereto. The wording “B was used instead of A” used in describing Synthesis Examples means that an amount of A used was identical to an amount of B used, in terms of a molar equivalent.

EXAMPLE Synthesis Example 1 Synthesis of Compound 1

Synthesis of Intermediate A

1.2 milliliters (mL) of THF was added to magnesium (0.48 grams (g), 20 millimoles (mmol)) at a temperature of 0° C. 1,3-dibromobenzene (4.9 g, 20.8 mmol) in 20 mL of THF solution was added dropwise thereto, and the resulting mixture was stirred until magnesium completely disappeared. Then, at a temperature of 0° C., diphenylphosphinic acid chloride (3.66 mL, 19 mmol) was added dropwise thereto. The resulting mixture was stirred at room temperature, and once the reaction was completed, 10% HCl was added thereto to perform hydrolysis. The reaction mixture was extracted using dichloromethane, the organic extracts were dried with magnesium sulfate, and the crude product obtained by removing a solvent by evaporation was purified by column chromatography (dichloromethane:ethanol) to obtain Intermediate A (1.64 g, 22%). The obtained compound was confirmed by MALDI-MS and HPLC analysis.

MALDI-TOFMS (m/z): C₁₈H₁₄BrOP (M⁺) 356.

Synthesis of Intermediate L1

To a solution of Intermediate A (6.42 g, 18 mmol) in 18 mL of THF was added iPrMgCl (in 2 molar (M) diethyl ether, 10.5 mL, 28 mmol) and at room temperature. The mixture was stirred for 2 hours, followed by the addition of Ni(dppp)Cl₂ (0.32 g, 0.6 mmol) and 2-bromo-1-methylpyridine (2.32 g, 24 mmol). The resulting mixture was stirred for 48 hours under reflux. Once the reaction was completed, a saturated ammonium chloride aqueous solution was added thereto to quench the reaction. The organic layer obtained by performing an extraction process twice thereon with 150 mL of difluoromethane was washed twice with 6 normal (N) HCl. The aqueous layer was neutralized and extracted with dichloromethane. An organic layer obtained therefrom was dried by using magnesium sulfate, and the crude product obtained by evaporating a solvent was purified by column chromatography (dichloromethane:ethanol) to obtain Intermediate L1 (0.96 g, 15%). The obtained compound was confirmed by MALDI-MS and HPLC analysis.

MALDI-TOFMS (m/z): C₂₄H₂₀NOP (M⁺) 369.

Synthesis of Intermediate B

2-phenylpyridine (14.66 g, 94.44 mmol) and iridium chloride (14.8 g, 41.97 mmol) were mixed with 210 mL of ethoxyethanol and 70 mL of distilled water. The resulting mixture was stirred under reflux for 24 hours to complete the reaction. Then, the temperature was lowered to room temperature. The resultant solid was separated by filtration, and thoroughly washed with water, methanol, and hexane in the stated order. The obtained solid was dried in a vacuum oven to obtain Intermediate B (20.2 g, 90%).

Synthesis of Intermediate C

Intermediate B (4.5 g, 4.20 mmol) was mixed with 60 mL of methylene chloride, and AgOTf (2.16 g, 8.41 mmol) dissolved in 20 mL of methanol was added thereto. Next, while being blocked from light by using an aluminum foil, the mixture was stirred at room temperature for 18 hours to complete the reaction. The generated solid was removed by celite filtration, and a filtrate was concentrated under reduced pressure. The obtained solid (Intermediate C) was used in the subsequent reaction without purification.

Synthesis of Compound 1

Intermediate C (5 g, 7.02 mmol) and Intermediate L1 (3.24 g, 8.77 mmol) were mixed with 70 mL of ethanol, and the resulting mixture was stirred under reflux for 18 hours to complete the reaction. Then, the temperature was lowered to room temperature. The resulting mixture was filtered to separate a solid, which was then thoroughly washed with ethanol and hexane. The product was purified by column chromatography with methylene chloride and hexane at a ratio of 35:65 to obtain 1.9 g (31%) of Compound 1. The obtained product was confirmed by Mass and HPLC analysis.

HRMS (MALDI-TOF) calcd for C₄₆H₃₅IrN₃OP: m/z 869.2147. Found: 869.2142.

Synthesis Example 2 Synthesis of Compound 2

Synthesis of Intermediate L2

1.0 g (15%) of Intermediate L2 was prepared in the same manner as Intermediate L1 in Synthesis Example 1, except that 2-bromo-4-methylpyridine (2.32 g, 24 mmol) was used instead of 2-bromo-1-methylpyridine.

MALDI-TOFMS (m/z): C₂₄H₂₀NOP (M+) 369.

Synthesis of Compound 2

1.8 g (29%) of Compound 2 was prepared in the same manner as Compound 1 in Synthesis Example 1, except that Intermediate L2 (3.24 g, 8.77 mmol) was used instead of Intermediate L1. The obtained product was confirmed by Mass and HPLC analysis.

HRMS (MALDI-TOF) calcd for C₄₆H₃₅IrN₃OP: m/z 869.2147. Found: 869.2145.

Synthesis Example 3 Synthesis of Compound 13

Synthesis of Intermediate D

2-(4-(trimethylsilyl))phenylpyridine (7.05 g, 33.07 mmol) and iridium chloride (5.18 g, 14.7 mmol) were mixed with 75 mL of ethoxyethanol and 25 mL of distilled water. The mixture was stirred under reflux for 24 hours to complete the reaction. Then, the temperature was lowered to room temperature. The resultant solid was separated by filtration, and thoroughly washed with water, methanol, and hexane in this stated order. The obtained solid was dried in a vacuum oven to obtain Intermediate D (9.01 g, 90%).

Synthesis of Intermediate E

Intermediate D (2.78 g, 2.04 mmol) was mixed with 60 mL of methylene chloride, and AgOTf (1.05 g, 4.08 mmol) dissolved in 20 mL of methanol was added thereto. Next, while being blocked from light by using an aluminum foil, the mixture was stirred at room temperature for 18 hours to complete the reaction. The generated solid was removed by celite filtration, and the filtrate was concentrated under reduced pressure. The obtained solid (Intermediate E) was used for the subsequent reaction without purification.

Synthesis of Compound 13

1.1 g (28%) of Compound 13 was prepared in the same manner as Compound 1 in Synthesis Example 1, except that Intermediate E (3.38 g, 3.95 mmol) was used instead of Intermediate C. The obtained product was confirmed by Mass and HPLC analysis.

HRMS (MALDI-TOF) calcd for C₅₂H₅₁IrN₃OPSi₂: m/z 1013.2938. Found: 1013.2936.

Synthesis Example 4 Synthesis of Compound 23

Synthesis of Intermediate F

2-(5-(methylD₃))phenylpyridine (8.74 g, 33.07 mmol) and iridium chloride (7.95 g, 22.5 mmol) were mixed with 120 mL of ethoxyethanol and 40 mL of distilled water. The mixture was stirred under reflux for 24 hours to complete the reaction. The temperature was then dropped to room temperature. The resultant solid was separated by filtration, and thoroughly washed with water, methanol, and hexane in this stated order. The obtained solid was dried in a vacuum oven to obtain Intermediate F (11 g, 86%).

Synthesis of Intermediate G

Intermediate F (4.59 g, 4.02 mmol) was mixed with 210 mL of methylene chloride, and AgOTf (2.07 g, 8.04 mmol) dissolved in 70 mL of methanol was added thereto. Next, while being blocked from light by using an aluminum foil, the mixture was stirred at room temperature for 18 hours to complete the reaction. The generated solid was removed by celite filtration, and a filtrate was concentrated under reduced pressure. The obtained solid (Intermediate G) was used for the subsequent reaction without purification.

Synthesis of Compound 23

2.04 g (28%) of Compound 23 was prepared in the same manner as Compound 1 in Synthesis Example 1, except that Intermediate G (6.01 g, 8.06 mmol) was used instead of Intermediate C. The obtained product was confirmed by Mass and HPLC analysis.

HRMS (MALDI-TOF) calcd for C₄₈H₃₃D₆IrN₃OP: m/z 903.2837. Found: 903.2834.

Synthesis Example 5 Synthesis of Compound 24

Synthesis of Intermediate H

Intermediate H (10.6 g, 83%) was prepared in the same manner as Intermediate F in Synthesis Example 4, except that 2-(4-(methylD₃))phenylpyridine (8.74 g, 33.07 mmol) was used instead of 2-(5-(methylD₃))phenylpyridine.

Synthesis of Intermediate I

Intermediate I was prepared in the same manner as Intermediate G in Synthesis Example 4, except that Compound H (8.74 g, 33.07 mmol) was used instead of Intermediate F.

Synthesis of Compound 24

Compound 24 (2.18 g, 30%) was prepared in the same manner as Compound 1 in Synthesis Example 1, except that Intermediate I (6.01 g, 8.06 mmol) was used instead of Intermediate C. The obtained product was confirmed by Mass and HPLC analysis.

HRMS (MALDI-TOF) calcd for C₄₈H₃₃D₆IrN₃OP: m/z 903.2837. Found: 903.2835.

Evaluation Example 1 Evaluation on HOMO, LUMO, and Triplet (T₁) Energy Levels

HOMO, LUMO and T₁ energy levels of Compounds 1, 2, 13, 23, and B to D were evaluated according to the method indicated in Table 2, and results thereof are shown in Table 3.

TABLE 2 HOMO energy level A potential (Volts, V) - current (Amperes, A) graph of each compound was evaluation method obtained by using cyclic voltammetry (CV) (electrolyte: 0.1M Bu₄NClO₄/ solvent: CH₂Cl₂/electrode: 3 electrode system (working electrode: GC, reference electrode: Ag/AgCl, auxiliary electrode: Pt)). Then, from reduction onset of the graph, a HOMO energy level of the compound was calculated. LUMO energy level Each compound was diluted at a concentration of 1 × 10⁻⁵ molar (M) in evaluation method CHCl₃, and an UV absorption spectrum thereof was measured at room temperature by using a Shimadzu UV-350 spectrometer, and a LUMO energy level thereof was calculated by using an optical band gap (Eg) from an edge of the absorption spectrum. T1 energy level A mixture of 2-methyltetrahydrofuran and each compound (each compound evaluation method was dissolved in an amount of 1 milligram (mg) in 3 cubic centimeters (cc) of toluene) was loaded into a quartz cell. Then, the resultant quartz cell was loaded into liquid nitrogen (77 Kelvins, K) and a photoluminescence spectrum thereof was measured by using a device for measuring photoluminescence. The obtained spectrum was compared with a photoluminescence spectrum measured at room temperature, and peaks appearing only at low temperature were analyzed to calculate T1 energy levels.

TABLE 3 HOMO (eV) LUMO (eV) Compound No. (found) (found) T₁ energy level (eV)  1 −5.100 −2.439 2.536  2 −5.091 −2.430 2.535 13 −5.060 −2.400 2.485 23 −5.048 −2.388 2.523 B −5.038 −2.502 2.398 C −5.039 −2.472 2.500 D −5.013 −2.493 2.480 Compound B

Compound C

Compound D

Referring to Table 3, it may be seen that absolute values of Compounds 1, 2, 13, and 23 are greater than those of HOMO of Compounds B through D.

Example 1

An ITO glass substrate was cut to a size of 50 millimeters (mm)×50 mm×0.5 mm, sonicated in acetone isopropyl alcohol and pure water, each for 15 minutes, and washed under exposure to UV ozone for 30 minutes.

Subsequently, on the ITO (anode) glass substrate, m-MTDATA was deposited at a deposition rate of 1 Angstroms per second (Å/sec) to form a hole injection layer having a thickness of 600 Angstroms (Å), and α-NPD was deposited on the hole injection layer at a deposition rate of 1 Å/sec to form a hole transport layer having a thickness of 250 Å.

Compound 1 (dopant) and CBP (host) were co-deposited on the hole transport layer at a deposition rate of 0.1 Å/sec and a deposition rate of 1 Å/sec, respectively, to form an emission layer having a thickness of 400 Å.

BAlq was deposited on the emission layer at a deposition rate of 1 Å/sec to form a hole blocking layer having a thickness of 50 Å, and Alq₃ was deposited on the hole blocking layer to form an electron transport layer having a thickness of 300 Å. Then, LiF was deposited on the electron transport layer to form an electron injection layer having a thickness of 10 Å, and Al was vacuum deposited on the electron injection layer to form a second electrode (cathode) having a thickness of 1,200 Å, thereby completing the manufacture of an organic light-emitting device having a structure of ITO/m-MTDATA (600 Å)/α-NPD (250 Å)/CBP+10% (Compound 1) (400 Å)/Balq(50 Å)/Alq₃(300 Å)/LiF(10 Å)/Al(1200 Å).

Evaluation Example 2 Evaluation on Characteristics of Organic Light-Emitting Devices

The organic light-emitting devices manufactured according to Examples 1 to 4 and Comparative Examples 1 and 2 were evaluated in terms of driving voltage, efficiency, power, color purity, quantum efficiency, and lifespan. Results thereof are shown in Table 4. This evaluation was performed using a current-voltage meter (Keithley 2400) and luminance meter (Minolta Cs-1000A). Lifespan (T₉₅, at 6000 nit) was evaluated by measuring the amount of time that elapsed until luminance was reduced to 95% of the initial brightness of 100%.

TABLE 4 Driving Lifespan Voltage Quantum (hr) Voltage Efficiency Power Efficiency (T₉₅, at Dopant (V) (cd/A) (Im/W) CIEx CIEy (%) 6000 nit) Example 1 Compound 1 3.6 42.6 37.2 0.306 0.598 18 40 Example 2 Compound 2 3.6 41.8 36.5 0.308 0.599 18 42 Example 3 Compound 13 4.0 48.8 38.3 0.316 0.602 19 51 Example 4 Compound 24 4.5 45.7 31.9 0.323 0.601 19 38 Comparative Compound A 3.7 37.6 32.2 0.316 0.599 18 30 Example 1 Comparative Ir(ppy)₃ 6.5 40.2 19.4 0.330 0.604 18 15 Example 2

Compound A

From Table 4, it was confirmed that the organic light-emitting devices prepared according to Examples 1 to 4 have lower driving voltage, higher efficiency, and longer lifespan than the organic light-emitting devices prepared according to Comparative Examples 1 and 2.

The organometallic compound according to embodiments has excellent electric characteristics and thermal stability. Accordingly, an organic light-emitting device including the organometallic compound may have excellent driving voltage, current density, efficiency, power, color purity, and lifespan characteristics.

It should be understood that exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each exemplary embodiment should typically be considered as available for other similar features or aspects in other exemplary embodiments.

While one or more exemplary embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims. 

What is claimed is:
 1. An organometallic compound represented by Formula 1:

wherein M in Formula 1 is selected from Ir, Pt, Os, Ti, Zr, Hf, Eu, Tb, Tm, and Rh, L₁ in Formula 1 is selected from ligands represented by Formula 2A, and n1 is 1, 2, or 3, and when n1 is 2 or greater, two or more groups L₁ are identical to or different from each other, L₂ in Formula 1 is selected from a monovalent organic ligand, a divalent organic ligand, a trivalent organic ligand, and a tetravalent organic ligand, and n2 is 0, 1, 2, 3, or 4, and when n2 is 2 or greater, two or more groups L₂ are identical to or different from each other, L₁ and L₂ in Formula 1 are different from each other, R₁, R₂ and R₁₁ to R₁₅ in Formula 2A are each independently selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, —SF₅, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted or unsubstituted C₂-C₆₀ alkynyl group, a substituted or unsubstituted C₁-C₆₀ alkoxy group, a substituted or unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀ arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q₁)(Q₂), and —B(Q₃)(Q₄), provided that at least one selected from R₁₁ to R₁₄ in Formula 2A is not hydrogen, b1 in Formula 2A is selected from 1, 2, 3, and 4, b2 in Formula 2A is selected from 0, 1, 2, and 3, each of * and *′ in Formula 2A indicates a binding site to M in Formula 1, and at least one of substituents of the substituted C₁-C₆₀ alkyl group, substituted C₂-C₆₀ alkenyl group, substituted C₂-C₆₀ alkynyl group, substituted C₁-C₆₀ alkoxy group, substituted C₃-C₁₀ cycloalkyl group, substituted C₁-C₁₀ heterocycloalkyl group, substituted C₃-C₁₀ cycloalkenyl group, substituted C₁-C₁₀ heterocycloalkenyl group, substituted C₆-C₆₀ aryl group, substituted C₆-C₆₀ aryloxy group, substituted C₆-C₆₀ arylthio group, substituted C₁-C₆₀ heteroaryl group, substituted monovalent non-aromatic condensed polycyclic group and substituted monovalent non-aromatic condensed heteropolycyclic group is selected from: a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, and a C₁-C₆₀ alkoxy group; a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, and a C₁-C₆₀ alkoxy group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q₁₁)(Q₁₂), and —B(Q₁₃)(Q₁₄); a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group; a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, a C₁-C₆₀ alkoxy group, a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q₂₁)(Q₂₂), and —B(Q₂₃)(Q₂₄); and —N(Q₃₁)(Q₃₂) and —B(Q₃₃)(Q₃₄), wherein Q₁ to Q₄, Q₁₁ to Q₁₄, Q₂₁ to Q₂₄, and Q₃₁ to Q₃₄ are each independently selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted or unsubstituted C₂-C₆₀ alkynyl group, a substituted or unsubstituted C₁-C₆₀ alkoxy group, a substituted or unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀ arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, and a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group.
 2. The organometallic compound of claim 1, wherein in Formula 1, M is Ir, and the sum of n1 and n2 is 3; or M is Pt, and the sum of n1 and n2 is 2, and the organometallic compound is not in the form of a salt.
 3. The organometallic compound of claim 1, wherein R₁ and R₂ in Formula 2A are each independently selected from: (A) a C₁-C₁₀ alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, and a 1,2,3,4-tetrahydronaphthyl group, each of which is unsubstituted; and (B) a C₁-C₁₀ alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, and a 1,2,3,4-tetrahydronaphthyl group, each of which is substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group.
 4. The organometallic compound of claim 1, wherein R₁ and R₂ in Formula 2A are each independently selected from: (A) a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, and a 1,2,3,4-tetrahydronaphthyl group, each of which is unsubstituted; and (B) a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, and a 1,2,3,4-tetrahydronaphthyl group, each of which is substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group.
 5. The organometallic compound of claim 1, wherein R₁ and R₂ in Formula 2A are each independently selected from: (A) a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a 1,2,3,4-tetrahydronaphthyl group, each of which is unsubstituted; and (B) a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, and a 1,2,3,4-tetrahydronaphthyl group, each of which is substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group.
 6. The organometallic compound of claim 1, wherein R₁₁ to R₁₅ in Formula 2A are each independently selected from: (A) a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, —SF₅, C₁-C₂₀ alkyl group, and a C₁-C₂₀ alkoxy group, each of which is unsubstituted; (B) a C₁-C₂₀ alkyl group and a C₁-C₂₀ alkoxy group, each of which is substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; (C) a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group, each of which is unsubstituted; (D) a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group, each of which is substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group; and (E) —N(Q₁)(Q₂) and —B(Q₃)(Q₄), wherein Q₁ to Q₄ are each independently selected from: (A) —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H and —CD₂CDH₂; (B) an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each of which is unsubstituted; and (C) an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each of which is substituted with at least one selected from a deuterium, a C₁-C₁₀ alkyl group, and a phenyl group.
 7. The organometallic compound of claim 1, wherein R₁₁ to R₁₅ in Formula 2A are each independently selected from: (A) a hydrogen, a deuterium, —F, a cyano group, a nitro group, —SF₅, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group and a pyrimidinyl group, each of which is unsubstituted; (B) a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group, each of which is substituted with at least one selected from a deuterium, —F, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a cyano group, a nitro group, a C₁-C₁₀ alkyl group, a C₁-C₁₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; and (C) —N(Q₁)(Q₂) and —B(Q₃)(Q₄), wherein Q₁ to Q₄ are each independently selected from: (A) —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and —CD₂CDH₂; (B) an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each of which is unsubstituted; and (C) an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each of which is substituted with at least one selected from a deuterium, a C₁-C₁₀ alkyl group, and a phenyl group.
 8. The organometallic compound of claim 1, wherein R₁₁ to R₁₅ in Formula 2A are each independently selected from a hydrogen, a deuterium, —F, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, groups represented by Formulae 9-1 to 9-17, and groups represented by Formulae 10-1 to 10-28, R₁ and R₂ in Formula 2A are each independently selected from: (A) a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group, each of which is unsubstituted; and (B) a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group, each of which is substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group:


9. The organometallic compound of claim 1, wherein L₁ is selected from ligands represented by Formulae 2A-1 to 2A-15:

wherein R₁₁ to R₁₄ in Formulae 2A-1 to 2A-15 are each independently selected from: (A) a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, —SF₅, C₁-C₂₀ alkyl group, and a C₁-C₂₀ alkoxy group, each of which is unsubstituted; (B) a C₁-C₂₀ alkyl group and a C₁-C₂₀ alkoxy group, each of which is substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; (C) a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group, each of which is unsubstituted; (D) a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group and an imidazopyrimidinyl group, each of which is substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group; and (E) —N(Q₁)(Q₂) and —B(Q₃)(Q₄), wherein Q₁ to Q₄ are each independently selected from: (A) —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and —CD₂CDH₂; (B) an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each of which is unsubstituted; and (C) an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each of which is substituted with at least one selected from a deuterium, a C₁-C₁₀ alkyl group, and a phenyl group, and R₁, R₂, R₁₅, b1, and b2 are the same as in claim
 1. 10. The organometallic compound of claim 1, wherein L₁ in Formula 1 is selected from ligands represented by Formula 2A(1):

wherein R₁, R₂, and R₁₁ to R₁₄ in Formula 2A(1) are the same as in claim 1, and R_(15a), R_(15b), and R_(15c) are the same as R₁₅.
 11. The organometallic compound of claim 1, wherein L₁ is selected from ligands represented by Formulae 2A(1)-1 to 2A(1)-15:

wherein in Formulae 2A(1)-1 to 2A(1)-15, R₁₁ to R₁₄ are each independently selected from: (A) a deuterium, —F, a cyano group, a nitro group, —SF₅, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group, each of which is unsubstituted; (B) a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group, each of which is substituted with at least one selected from a deuterium, —F, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a cyano group, a nitro group, a C₁-C₁₀ alkyl group, a C₁-C₁₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; and (C) —N(Q₁)(Q₂) and —B(Q₃)(Q₄), R_(15a), R_(15b), and R_(15c) are each independently selected from: (A) a hydrogen, a deuterium, —F, a cyano group, a nitro group, —SF₅, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group, each of which is unsubstituted; (B) a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group and a pyrimidinyl group, each of which is substituted with at least one selected from a deuterium, —F, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a cyano group, a nitro group, a C₁-C₁₀ alkyl group, a C₁-C₁₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; and (C) —N(Q₁)(Q₂) and —B(Q₃)(Q₄), R₁ and R₂ are each independently selected from: (A) a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group, each of which is unsubstituted; and (B) a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group and a carbazolyl group, each of which is substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group, and wherein Q₁ to Q₄ are each independently selected from: (A) —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and —CD₂CDH₂; (B) an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each of which is unsubstituted; and (C) an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each of which is substituted with at least one selected from a deuterium, a C₁-C₁₀ alkyl group, and a phenyl group.
 12. The organometallic compound of claim 1, wherein L₂ in Formula 1 is selected from ligands represented by Formulae 3A to 3G:

wherein in Formulae 3A to 3G, Y₁₁ to Y₁₆ are each independently selected from carbon (C) or nitrogen (N), Y₁₁ and Y₁₂ are linked to each other via a single bond or a double bond, Y₁₃ and Y₁₄ are linked to each other via a single bond or a double bond, Y₁₅ and Y₁₆ are linked to each other via a single bond or a double bond, CY₃ to CY₅ are each independently selected from a C₅-C₆₀ cyclic group and a C₂-C₆₀ heterocyclic group, a1 to a3 are each independently an integer selected from 1 to 5; A₁ is P or As; X_(11a), X_(11b), X_(12a), X_(12b), X_(13a), and X_(13b) are each independently selected from N, O, N(R₃₄), P(R₃₅)(R₃₆), and As(R₃₇)(R₃₈) (provided that X_(12a), X_(12b), X_(13a), and X_(13b) are neither N nor O); R_(33″) and R_(34″) are each independently selected from a single bond, a double bond, a substituted or unsubstituted C₁-C₅ alkylene group, a substituted or unsubstituted C₂-C₅ alkenylene group, and a substituted or unsubstituted C₆-C₁₀ arylene group; Z₁ to Z₃, R₃₁, R_(32a), R_(32b), R_(32c), R_(33a), R_(33b), R₃₄ to R₃₈, R_(35a), R_(35b), R_(35c), and R_(35d) are each independently selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted or unsubstituted C₂-C₆₀ alkynyl group, a substituted or unsubstituted C₁-C₆₀ alkoxy group, a substituted or unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀ arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q₁)(Q₂), —B(Q₃)(Q₄), —Si(Q₅)(Q₆)(Q₇), and —P(═O)(Q₈)(Q₉), each of * and *′ indicates a binding site to M in Formula 1, and at least one of substituents of the substituted C₁-C₅ alkylene group, substituted C₂-C₅ alkenylene group, substituted C₆-C₁₀ arylene group, substituted C₁-C₆₀ alkyl group, substituted C₂-C₆₀ alkenyl group, substituted C₂-C₆₀ alkynyl group, substituted C₁-C₆₀ alkoxy group, substituted C₃-C₁₀ cycloalkyl group, substituted C₁-C₁₀ heterocycloalkyl group, substituted C₃-C₁₀ cycloalkenyl group, substituted C₁-C₁₀ heterocycloalkenyl group, substituted C₆-C₆₀ aryl group, substituted C₆-C₆₀ aryloxy group, substituted C₆-C₆₀ arylthio group, substituted C₁-C₆₀ heteroaryl group, substituted monovalent non-aromatic condensed polycyclic group, and substituted monovalent non-aromatic condensed heteropolycyclic group is selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, and a C₁-C₆₀ alkoxy group; a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, and a C₁-C₆₀ alkoxy group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q₁₁)(Q₁₂), —B(Q₁₃)(Q₁₄), —Si(Q₁₅)(Q₁₆)(Q₁₇), and —P(═O)(Q₁₈)(Q₁₉); a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group; a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, a C₁-C₆₀ alkoxy group, a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q₂₁)(Q₂₂), —B(Q₂₃)(Q₂₄), —Si(Q₂₅)(Q₂₆)(Q₂₇), and —P(═O)(Q₂₈)(Q₂₉), and —N(Q₃₁)(Q₃₂), —B(Q₃₃)(Q₃₄), —Si(Q₃₅)(Q₃₆)(Q₃₇), and —P(═O)(Q₃₈)(Q₃₉), wherein Q₁ to Q₉, Q₁₁ to Q₁₉, Q₂₁ to Q₂₉, and Q₃₁ to Q₃₉ are each independently selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted or unsubstituted C₂-C₆₀ alkynyl group, a substituted or unsubstituted C₁-C₆₀ alkoxy group, a substituted or unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀ arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, and a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group.
 13. The organometallic compound of claim 1, wherein L₂ in Formula 1 is selected from ligands represented by Formulae 3-1 to 3-111:

wherein in Formulae 3-1 to 3-111, Z₁, Z₂, Z_(1a), Z_(1b), Z_(2a), Z_(2b), Z_(2c), R_(34a), R_(34b), and R_(34c) are each independently selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, —SF₅, C₁-C₂₀ alkyl group, and a C₁-C₂₀ alkoxy group; a C₁-C₂₀ alkyl group and a C₁-C₂₀ alkoxy group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group and an imidazopyrimidinyl group; a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group and an imidazopyrimidinyl group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group; and —N(Q₁)(Q₂), —B(Q₃)(Q₄), —Si(Q₅)(Q₆)(Q₇), and —P(═O)(Q₈)(Q₉), wherein Q₁ to Q₉ are each independently selected from —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and —CD₂CDH₂; an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group; and an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each substituted with at least one selected from a deuterium and a C₁-C₁₀ alkyl group, aa2 and ab2 are each independently 1 or 2, aa3 and ab3 are each independently an integer selected from 1 to 3, aa4 and ab4 are each independently an integer selected from 1 to 4, and each of * and *′ indicates a binding site to M in Formula
 1. 14. The organometallic compound of claim 1, wherein L₂ in Formula 1 is selected from ligands represented by Formulae 3-1(1) to 3-1(59) and 3-111:

wherein in Formulae 3-1(1) to 3-1(59) and 3-111, Z₁, Z₂, Z_(1a), Z_(1b), Z_(1c), Z_(1d), Z_(2a), Z_(2b), Z_(2c), Z_(2d), R_(34a), R_(34b), and R_(34c) are each independently selected from a deuterium, —F, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, —Si(Q₅)(Q₆)(Q₇), groups represented by Formulae 9-1 to 9-17, and groups represented by Formulae 10-1 to 10-28, and wherein Q₅ to Q₇ are each independently selected from —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and —CD₂CDH₂; an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group; and an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each substituted with at least one selected from a deuterium and a C₁-C₁₀ alkyl group:


15. The organometallic compound of claim 1, wherein in Formula 1, M is Ir and the sum of n1 and n2 is 3; or M is Pt and the sum of n1 and n2 is 2, the organometallic compound is not in the form of a salt, and L₁ in Formula 1 is selected from ligands represented by Formulae 2A(1)-1 to 2A(1)-15, and L₂ in Formula 1 is selected from ligands represented by Formulae 3-1(1) to 3-1(59):

wherein in Formulae 2A(1)-1 to 2A(1)-15, R₁₁ to R₁₄ are each independently selected from a deuterium, —F, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CFH₂, groups represented by Formulae 9-1 to 9-17, and groups represented by Formulae 10-1 to 10-28, R_(15a), R_(15b), and R_(15c) are each independently selected from a hydrogen, a deuterium, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, groups represented by Formulae 9-1 to 9-17, and groups represented by Formulae 10-1 to 10-28, R₁ and R₂ are each independently selected from a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, and a 1,2,3,4-tetrahydronaphthyl group; and a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, and 1,2,3,4-tetrahydronaphthalenyl group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —CD₃, —CD₂H, —CDH₂, —CF₃, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group; and in Formula 3-1(1) to 3-1(59), Z₁, Z₂, Z_(1a), Z_(1b), Z_(1c), Z_(1d), Z_(2a), Z_(2b), Z_(2c), and Z_(2d) are each independently selected from a deuterium, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, —Si(Q₅)(Q₆)(Q₇), groups represented by Formulae 9-1 to 9-17, and groups represented by Formulae 10-1 to 10-28, Q₅ to Q₇ are each independently selected from —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and —CD₂CDH₂; an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group; and an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each substituted with at least one selected from a deuterium and a C₁-C₁₀ alkyl group:


16. The organometallic compound of claim 1, wherein the organometallic compound is one of Compounds 1 to 30:


17. An organic light-emitting device comprising: a first electrode; a second electrode; and an organic layer disposed between the first electrode and the second electrode, wherein the organic layer comprises an emission layer and at least one organometallic compound of claim
 1. 18. The organic light-emitting device of claim 17, wherein the first electrode is an anode, the second electrode is a cathode, and the organic layer comprises: i) a hole transport region disposed between the first electrode and the emission layer, wherein the hole transport region comprises at least one of a hole injection layer, a hole transport layer, and an electron blocking layer, and ii) an electron transport region disposed between the emission layer and the second electrode, wherein the electron transport region comprises at least one selected from a hole blocking layer, an electron transport layer, and an electron injection layer.
 19. The organic light-emitting device of claim 17, wherein the emission layer comprises the organometallic compound of claim
 1. 20. The organic light-emitting device of claim 19, wherein the emission layer further comprises a host, a highest occupied molecular orbital energy level of the host is in a range of about −5.3 electron Volts to about −5.8 electron Volts, a lowest unoccupied molecular orbital energy level of the host is in a range of about −1.6 electron Volts to about −2.0 electron Volts, and a T₁ energy level of the host is in a range of about 2.7 electron Volts to about 2.9 electron Volts. 